Repowering with a Yanmar 2GM20

[Triton106]

After years of discussion and who knows how many changes of ideas I finally decided to repower Blossom with a diesel - a Yanmar 2GM20. The Atomic 4 is running smoothly and I have always taken a good care of the engine. The primary reason I decide to repower now rather than waiting until when I am ready to cast off the shorelines for the fair maidens and green hills over yonder is that I found a very good deal with a slightly used 2GM20 for a reasonable price locally in San Francisco. Other options I have considered include (1) outboard in a well - similar to what James Baldwin did on Salty, (2) sail engineless (or with an outboard on the bracket as an emergency measure), or (3) keep the A4 going indefinitely. This thread is not meant to reopen the discussion of diesel vs gas engine. I plan to document my repowering process here for discussion and sharing.

Step 1 - swapping out the A4 with the Yanmar.

The following is what I posted on Moyer Marine Forum on the first step:

There is no easy way to say it, I have gone to the dark side. I ran my beloved Atomic 4 for the last time on Saturday in the dock for 20 mins. The engine ran beautifully as it always did. Water temp 150, oil pressure 35, compressions 90+, battery fully charge, tach read 1800 RPM. I shut it down for the last time (in Blossom), drained the oil that I just changed a month ago, disassembled fuel, cooling, exhaust, and electrical systems. I disconnected the control cables, unbolted the starter, alternator, and coil to prepare it for unloading.

On Sunday my friends Rob and Luke showed up at 2:30PM sharp and we lifted it off Blossom with the boom and swang it to the dolly on the dock and wheeled it to Rob's van. We then unloaded my new to me Yanmar 2GM20 from Luke's van and wheeled it to the dock and reversed the process. The Yanmar is now sitting on the cabin sole waiting to be installed...

[Triton106]

Step 2 - rebuilding the engine stringers.

The Yanmar footprint is approximately 14.5" wide vs. the A4 footprint of 11.5". That means I need to rebuild the engine stringers to accommodate the wider stance of the Yanmar. I am considering the following approach - sister a piece of 1.5" wide oak or other appropriate hardwood plank to the outside of the existing stringer and add a 1" thick plank on top to tie the two together so that the engine mounting bolts will not drive into the gap between the two planks. The Yanmar engine mounts also sits approximately 1/4" lower than the Atomic 4 which means that I will need to cut the existing stringer 1-1/4" to account for the lower engine mounts and the extra plank I plan to glue on top.

Here is a picture from the Naitonal Triton Association website that shows how Head Over Heels does it. The owner Rob Squire also repowered with a Yanmar 2GM20 with the exactly same dimension.



Here is a picture of Blossom's stringers during a rebuild a couple of years ago.



Another issue I am struggling with is that the wider Yanmar stance and longer engine mount base do not allow the Yanmar to sit as far back as the Atomic 4 (by about 3"). This is in turn creating other problems - (1) it means I will not be able reuse the prop shaft, (2) it will force me to move the companion way ladder forward and interfere with the standing room in the galley. These aren't insurmountable problems but I would rather not have to do deal with them. To address the issue I plan to (a) cut off a small piece of the Yanmar rear mount corners to enable them to be moved as far back as possible (by about 1"), (b) add an flexible coupling (about 1") - something I want to do anyway, (c) pull the propeller shaft foward about 1" (the shaft is long enough to accommodate that). These three measures should take care of the problem and allow me to reuse the prop shaft.

[TritonSean]

Interesting !

please send more photos, especially of your exhaust hook-up when you get there.

"head over heels" setup looks much like Jenny Marie's - We have a box for the starting battery and spare engine parts which is very convenient.
Jenny has a Universal M25XP

[tpl]

> cut...the Yanmar...mount corners

or you could use smaller mounts on the back--we use Vetus on
our 3GM30

[Triton106]

> cut...the Yanmar...mount corners

or you could use smaller mounts on the back--we use Vetus on
our 3GM30

Thanks TPL, I thought about that. I tried to talk the seller into swapping the Yanmar mounts for R&D or other manufacturers' mounts but to no avail. But there is no sense in spending $200-$300 for smaller mounts as the Yanmar mounts are in excellent condition.

Here are picture/drawing of the Yanmar vs. R&D mounts. I plan to round off the corner of the rear mounts to shape them similar to the R&D mounts so I can move the engine back about 1".

[Tallystick]

Save yourself some of the grief I put myself through, and make yourself a template for your new engine's footprint to use for fabricating your engine stringer modifications.

[Triton106]

Thanks Tallystick! I totally plan to do that. Here is a famous quote from the MAN (of course I am referring to Tim Lackey)

Moving into the cockpit, I reached through the access hatch there and pulled the shaft forward to check the rough alignment. The couplings thunked together nicely, indicating that the alignment was very close. The side-to-side and up-and-down alignment seemed spot on, so all I had to worry about was the fine face alignment of the couplings. Using a feeler gauge, I checked the coupling alignment all the way around, and made some small adjustments to the engine. It didn't take much--the alignment template is worth its weight in platinum[emphasis added], and is certainly worth the effort required to build it.

- from the log of Glissando rebuild project.



Here is my attempt - not quite the same workmanship as Tim but serves the purpose nonetheless. Sorry about the poor photo quality - I used my BlackBerry.



I laid it over the existing stringer (see previous post) and confirmed that I need to widen the stringer by 2" (not 1.5" as I thought before) and lower it by 1-1/4" (to account for Yanmar's lower engine mount and the 1" plank I will overlay the existing stringer and the addition.). It also confirmed for me that there is a 2.5" gap between the shaft coupling and the engine coupling. As mentioned before I plan to close that gap by rounding off the rear mount corner (to accommodate where the rising hull is interfering) and adding a flexible coupling from R&D.

[Triton106]

Sunday, February 5, 2012 -

Today I focused on milling the stringers and the top overlay pieces. I rought cut them and my friend Rob helped me shape, sand, and router over the edges. They took much longer than I expected (don't they always?) Here are some pictures of the finished products. They don't look much but should be strong enough for the job.

The bottom stringers are milled from white oaks, bought for $27 from McBeath -



The top overlay pieces are milled from mahogany I happend to have around -



The Yanmar rear mounts with corners rounded off so that the engine can be situated as far back as possible -



The template is placed on the stringers temporarily for fitting test. The stringer heigher, width, and angle appear to be right.



The shaft coupling and engine coupling are still 1.5" apart as expected. I plan to use a R&D flexible coupling to close that gap.




Next weekend I plan to epoxy the stringers in place and then glass over them. This is a project for training my patience... Luckily I have some experience from my last stringer repair job two year ago. Engine Vibrating Excessively

[Crazer]

Looking good! Thanks for sharing the step-by-step.

[Triton106]

I glassed in the stringers this weekend. That's about it. These things always take 2-3 times as long as I would think. Kids violin performances and other family commitment eat up the rest of the weekend. I will post the pictures of the finished stringer next week (forgot to bring the camera again).

[bigd14]

Looking good! It always sounds so easy, doesn't it? I'll just swap this engine out...

[Triton106]

Well, if you thought I gave up on this project I don't blame you. But what actually happened is that I decided to do it the "right" way - i.e. to take this opportunity to replace the cutless bearing, prop shaft coupling, stuffing box hose. I also inspected the prop shaft and the stuffing box which seem to be in pretty good condition. However, in order to do that I need to wait for a clear weather window to haul the boat out. It did not rain much here in the winter this year but it rained, rained, and rained in February, then March, then April...

Finally, I got a week window without rain and haul the boat out at the local boatyard, Svendsens. I had the boat in the sling overnight, thinking that me and a couple friends can pop the old parts out and pop the new ones in in a couple of hours. Well, let's just say it was not that easy. To make the long story longer we had to have the boatyard replace the propeller (13"x13" 3 fixed blades) and the cutless bearing. I was able to pull the shaft coupling off myself using a harmonic balance puller.

I learned a couple of interesting facts about the Triton (at least the west coast version) -

1) The cutless bearing has no set screws! I sanded and sanded the stern tube for over half an hour and could not find a single trace of set screw until Rod (the boatyard guy) brough back the new prop, which is now installed on the shaft, and said that some boats just don't have set screws. My friends Luke and Rob decided that since we have the pro here why waste their valuable beer drinking time to pull the cutless bearing ourselves. Seeing that he could not make a getaway (since we basically had him surrounded and weren't going to let him leave without replacing the cutless bearing) Rod instructed us to make two cuts in the cutless bearing (90 degrees to each other, one at 6 o'clock the other at 9 o'clock). While we made the cuts (which is very easy to do since the bearing is made of brass or bronze) he went back and fetch his slide hammer. It literally took him all but five minutes to hammer the bearing out.

Here is Rod showing me the stuffing box in a good condition -

[Triton106]

2) The cutless bearing is not full length - the old bearing is about 3" instead of the 4" length of the new one. Rod explained that when you insert the new bearing back in the stern tube you don't want the hammer it in too hard for it will be very difficult to take it out again. So after sanding the stern tube clean and solven washed it Rod gentally hammer the new bearing into the stern tube with a soft wood block to cushion the hammer blow. When it was 3/4 way in he cut off the remaining 1" flush against the end of the stern tube. This explains why the old one is only 3" long.

Here the prop and prop shaft is reinstalled in the stern tube after the bearing is replaced. You can see the sanding and cisel marks on the stern tube which I later epoxied and repainted.


3) The stern tube is bronze embedded in fiberglass - this is nice since I would not be as concerned about cracking it when I tighten down the stuffing box hose clamps on the inside part of the stern tube.

With Rod's help I had some extra time left in the day to give the area under the water line another coat of anti fouling paint. Since I just redid the bottom last year I did not need to repaint the entire bottom again this year. But it was nice to renew paint right under the water line, especially the rear of the boat which has been sitting a lot higher than the water line because I have removed the 300+ lb Atomic 4 and the 200+ lb Yanmar 2GM20 is now sitting in the middle of the cabin sole.

Here my friend Rob Heggen is taping up the waterline -

[Triton106]

Well, the story did not just end there. Toward the end of the day after Rod and Rob both left I realized that I have not installed the new shaft coupling!!! So, in the near darkness Luke and tried to finish it that evening (even as the temperature was significantly cooling down!) since the boat was scheduled to be launched the next morning. I first tried to install the coupling with the key on the shaft key way. But as I slowly hammered the coupling in the key just gets pushed out along the inclining portion of the shaft key way. Frustrated I pulled the coupling off again and tried to install it with the key in the coupling key way this time. Again, as I slowly hammer it in the key was getting pushed out of the coupling this time! Luke and I were just cold and exhausted. We decided to let the boatyard do it the next morning.

With a nice hot chicken soup and a good night's sleep my attitude was far more positive in the morning. After talking to the travel lift operator and asked (begged) that he work on two other boats first (the boatyard has two travel lifts) I asked the yard manager to send someone to help me with installing the coupling. So they sent Amolia who had worked on my stuffing box last year. It took him about 10 mins to install the coupling, most of the time he actually spent modifying the key so it fits the inclining portion of the shaft key way. He also used plenty of anti seizing compound between the shaft and the coupling.

Here the coupling is happily mated to the shaft -



The following weekend Rob and I installed the engine mounts on the Yanmar and test fitted the engine on the new stringers and the distance between the engine half of the coupling, the flexible coupling, and the new shaft coupling. Happily my calculation was pretty accurate. The only thing that required modifcation was the engine mounts which I had trimmed before to enable the to sit as far aft as possible. But they still did not sit flush against the stringers. But all it required was that I trim off the corner of the mounts a wee bit more. We marked the engine mount locations and removed the engine from the stringers.

The next day I drilled the stringers and installed four coupling nuts in each stringer to accept engine mount bolts. I then repainted the stringers.

[Triton106]

A few notes on the west coast Triton drivetrain parts dimensions:

1. Shaft - 7/8" stainless steel
2. Shaft Coupling (solid) - ID = 7/8", Flange diameter = 4", length = 2-1/4" (Buck Algonquin part number 50mcy004 for Yanmar 2GM20)
3. Flexible Coupling - diameter = 4.5", length = 1.28" (R&D Marine part number 910-002)
4. Cutless Bearing - inside diameter = 7/8", outside diameter = 1-3/8" (Buck Algonquin part number APEX)
5. Stern Tube - inside diameter = 1-3/8", outside diameter = 1-3/4"
6. Backing Box Hose - inside diameter = 1-3/4", outside diameter = 2-3/8", length = 4-1/2" (Buck Algonquin part number 80ho175)
7. Stuffing Box - shaft size = 7/8", packing box hose ID = 1-3/4", packing size = 5/16" (Buck Algonquin part number 00pb88)
8. Propeller - 3 blade, right hand, 13"x13" bronze

[Triton106]

Well, that was about 10 months ago. The repower project was completed a few months ago. For whatever reason I procrastinated and did not finish posting the project here. A few days ago another Bay Area sailor Brad Low contacted me because he is in the process of repowering his Islander 29 and wanted to learn from my experience. Separately, I was helping my friend Rob Heggen to repower his Atomic 4 with my old Atomic 4 on Saturday (I gave Rob my old Atomic 4 which was running in tiptop condition in exchange for his help with my repower project). These two unrelated events reminded me that I need to finish my project posting here.

Determining the location, height, and angle of the engine stringers and building them is probably the most challenging aspect of the project. The rest of it went pretty smoothly. Resuming where I left off in the last post Rob and I loaded the Yanmar on the stringers. Before that I already determined and set the adjusting nuts on the engine mount to about 1/3 of the distance from the bottom of the threads. Once the engine is properly sitting on the stringers I roughly aligned the engine before bolting the the engine mounts to the stringers (just hand tight since I need to fine tune the aglignment). That completed I fine tuned the alignment. The up and down and angle alignment is pretty straight forward. The challenging part is to align the engine coupling face to the shaft coupling in the athwartship direction because the limited mobility created as a result of the mounts having slots drilled only on one end of it. The other end is just a round hole about 1/2" and the bolts I used are 3/8". After a few attempts I settled with the athwartship aligned to within 9/1000" which is barely in the acceptable range (due to the additon of the flexible coupling the alignment tolerence is increased from 4/1000" to 10/1000".) I need to realign the engine after running it for 50 hours and hope to do a better job next time. Here a couple of pictures of the engine sitting in the engine bay. Pretty snug fit.

[Triton106]

Once the alignment job is done connecting fuel, water and exhaust systems went pretty smoothly and were uneventful. The electrical harness that came with the engine was heavily corroded since it had been sitting in the boatyard for the last ten years or so unused. I had to painstakingly sand out the tiny little connectors and spray them with CorrosionX. It worked just fine after that.

Another project I completed during the repower project is to replace my old engine control panel with the Yanmar B type panel that came with the engine. The face plate was cracked and corners broken off. So I ordered another face plate from the local boatyard Svendsens that recently became an authorized Yanmar dealer. Before installing it I decided that I want to build a recessed enclosure for the control panel so that the key and switches do not get in the way of the lines and sheets in the cockpit. What my friend Rob said was a weendend project turned into like a four weekend project. Ultimately I was satisfied with the outcome which is what mattered. Here is a picture of the instrument panel in the recessed bulkhead. I have not installed the wooden enclosure yet but I have built the enclosure. As you can see I added a water temperature and oil pressure gauge to the standard Yanmar type B instrument panel. I think these two gauges are pretty important.

[Triton106]

The next significant project is the installation of the gear control unit. Years ago anticipating that one day I would repower with a diesel engine I bought a used Moorse gear control unit from a closeout sale for something like $70/$80. But the unit was missing a few things like the brackets that hold the control cable to the control unit, the control cable pivots, and more importantly the cover plate (that protects the unit from sea spray that finds it ways into the cockpit). Buying these parts from the dealers would add significantly to the cost. So I ended up spending several weekends finding parts I can get from hardware stores and McMasterCarr as a surrogates for the brackets but did have to buy the pivots which are not that expensive. I decided to forego the cover plate and instead I drilled a large enough hole in the cockpit bulkhead that the shaft of the shift control bare passes through. Even if sea spray does board the cockpit not much of it will get through. Here is a picture of the final control unit inside and outside as well as the engine stop control. My friend Rob likes to point out that it is really easy for someone to accidently turn off the engine key instead of pulling on the engine stop cable to stop the engine. In that case the alternator will likely be damaged. I would be interested in anyone who has any idea to prevent that other than just not inviting dumb crew to go sailing with you.

[Triton106]

Well, the repower project is now completed. It was pretty amazing that after connecting all of the systems my friend Luke was there to help me with firing up the Yanmar for the first time. I did not even know if the starter would kick over but on first push of the engine starting button the Yanmar roared into life. This machine has been sitting in the boatyard for 10 years! It's absolutely amazing. Unfortunately the motor only ran for a few minutes because the diesel line had not been properly bled. So a bleeding lesson from Luke ensued. I made the beginner's mistake of tightening the bleeding screw with a wrench and broke off the screw head. Fortunately Svendsens carries them. The new bleeding screw has a new design which instead of a hollowed inside it has a groove along the side of the thread which make it a little stronger and can't be broken off as easily. Apperently it happens to Yanmar novice users a lot.

Lately I have been motoring quite a bit with the new to me Yanmar. I have to say I am pretty happy with the outcome on the whole. It always fires up on the first try and runs without any complaints. The only two areas I want to mention are - prop size and impact on steering. Before purchasing the prop I talked to several prop shops and most of them recommended for Pearson Triton and Yanmar 2GM20 13"x12" 3 blade props. I looked around for a used one and was able to find an old but never used 13"x13" 3 blade in a local marine consignment store. It was less than $200 so it is a deal I could not refuse so to speak. During my test runs I was never able to get the rpm above 3000 (Yanmar spec is 3600). Since I just installed the prop I know it could not be that is due to marine growth. It has to be over proped. A couple of months ago I found a 13"x12" 2 blade prop in the same store. This one is slightly used but still in a very good condition. I bought it for something like $80. I plan to swap out the 3 blade prop for this one the next time I haul out. I will then have a prop shop repitch the 3 blade to 13"x12". I hope that will fix the low max rpm issue.

The other issue is that once I rev up the engine to over 2000 I notice a not insignificant amount of resistance on the tiller when I am just going straight. It could be that the prop is too large for the apeture between the hull and rudder. Do you all have similar experience with your engines? It's not that big of a deal but sure would be nice if I can motor for an hour without my hand getting sore from having the hold the tiller tightly to keep the boat going in a straight line.

Well, this is about all I have to report on the repower project. My overall conclusion is that I am glad I have done it. Would I do it over again in the same way instead of going with an outboard with a well in the lazerette (similar to James Baldwin's concept). I don't know. But probably will not have to worry about that question for as long as I own Blossom.

[earlylight]

Congrats on a job well done.