Yanmar 4LH 160/170 in B26 or B28

[Joef]

Hey guys - anyone have or know of someone with 4LH 160/170hp engines in their B28 or b26? My dad purchased a b26 sport convertible (straight inboard) w 4.3 v6 crusaders. Engines are in decent shape but need cleaning , some
Money and lots of love. In the hazy moments that sometimes happens when you spend too much time thinking about something, we started to wonder about replacement engines and diesel options. 25 years of cat 3208s in our last boat and you kinda miss the whiff of diesel in the morning. I would guess the yanmar 4lh engines would fit in those engine boxes pretty well- I’ve see some v8 5.7l repowers and n those boats. I’ve seen some used 4lh engines and to avoid needing to replace the entire drive train, there’s some advantage to staying w the lower HP version - do you think you can push a b26 to 20-22’ish knots w twin 160hp diesels? I kinda think you could. I don’t imagine there will be many folks w diesels in theses 26s but might be one of you w them in a b28

Joef

[Tony Meola]

Joe

My friend has them in his 28. Pushes it along pretty good. He has no complaints.

[Yannis]

The 160's in a 28 is marginal.
I have the 240's and its about right.

[Bruce]

I repowered a few 28's with Yanmar 4 bangers.
The 160/170 is workable on a very lightly loaded non wet 28. I always pushed for the 230. One customer insisted on the 170 and I did it, Customers always right?

Sea trial came and it did okay, light fuel, 2 guys, not much gear but took a little long to get up on plane but did. I saw it but customer was okay with it.
Month and a half later I get a call that the boat won't plane and is black smoking. I said bring it by the marina and I'll take a look. Took it out, did the same as sea trial. Perplexed.
Took it home. Monday past weekend get the same call. I said bring it by only have it loaded as you did on weekend. Guys says I can't because my 3 friends and their scuba gear and ice chests aren't available.
Customer had no clue so I told him to come by the office and we had a heart to heart and he got it then. He asked what I could do and I said I'd take the engines on a trade in for the 230's. But he expected to get full value and when I explained they were used and the price I offered on trade in was not satisfactory I shrugged my shoulders and said oh well.
He left and he sold the boat a couple of months later and lost his ass as it was under powered. Guy who bought the boat, yanked the engines for his small commercial fishing boat, sold the 28 hull for what he paid for the whole thing and got the engines with less than 50 hours on them for free.

[Carl]

Bruce-

What if the wheel pitch was reduced to offset the heavy load? Yes, I'd be slow and underpropped when light, but maybe at least it would get on plane and hit rated WOT when heavy. Underpowered is what it is...

In my head, I'm thinking about the 4-53's @ 140hp in the 31. Yes slow, but they'd get on plane and go with motors lasting many many moons.

[SteveM]

I had a 26 Sport Convertible, but the one with the open transom built in the factory for outboards. It had twin 150 Johnsons. It flew and rode great. Sometime I wish I still had it. I have seen the same as your boat converted with a bracket, they are nice. I have Yanmar 6LP's in my 31. You won't get the same diesel smell in the morning as you did with your old CAT's Nothing wrong with new gas inboards in that boat either. That is likely your least expensive route. Just use your blower.

[Tony Meola]

I will say my friends 28 transom is black by the end of the season. I put more hours on mine than he does and mine stays pretty clean. I do have to give it a good cleaning in the fall but from 5 feet away it looks clean.

I had attributed it yanmars smoke but maybe they are working too hard.

[Yannis]

Bruce,

The 240/250 hp 4LHA's are declared as such (with two hp values) because, I believe, of the temperature of the diesel fuel. The cooler the fuel the higher the hp value.
I noticed you mentioned 230's. Is this another motor, another fuel temp, or US emission standards?
Thanks.

[DanielM]

The other thing to think about is the B26 should be considerably lighter overall than the B28. Maybe the 170s would be adequate for a B26 if there is room to swing a big enough prop that you might need for the diesels. Also I don’t know about the weight difference between the Yanmar 170 and the gas engines. Might make it too heavy in the back. UV posted years ago about having a B25 with Volvo diesels and I think his scuppers were close or maybe under the water line IIRC. You might want to think about that.

All that being said, gas inboards are surely the best cheapest quickest route and gas engines have been good for that boat up until now.

Good luck. It’s an interesting thought.

[DanielM]

It just dawned on me the B26 is straight inboard vs UVs sterndrive B25. A little additional engine weight might be insignificant where those engines set.

[Carl]

I may be wrong but it looks like Daniel was the 1st to pick up on the fact it would be a B26 installation. If marginal in a 28 I'd think they would be more than adequate in a 26.

As you said, the running gear may be adequate to handle a high reving diesel which saves a bunch of money and time. True a bigger wheel and reduction is often the best performance direction, but it also leads to a more expensive and time consuming conversion.

I get the smile produced by burning diesel, is that the only reason if I can ask? I don't see performance being much better. Fuel economy, yeah I guess but how many hours before a return would be seen, especially with two motors. Range...sure thats a big plus. But a 26' boat where r you going. Safety...I guess, but gas I consider safe provided all precations are taken. Resale...beats me, is there a big market for 26' twin diesel boats. Smell... well if you wanna smell diesel your screwed as you have to go diesel...or maybe just buy a small diesel heater.

I ask as I used to enjoy listening to my dad try to explain to me why the Mitsubishi 4 banger diesel in his 17 or 18'' Chrysler ski boat was so great. I'll admit it burnt next to nothing, but from what I understand the original gas motor would have also burnt next to nothing too. Plus the original motor would not have required huge trim tabs to offset all that weight as it was an I/O. In the end, it was so great because he enjoyed the hell out of it producing a continuous smile as he cruised around the Island, to Manhatten for coctails, City Island to say hey, up the Hudson becasue it was there.

[ktm_2000]

my 25 goes quite nicely with a single 300hp outboard. cruises 25kts at 10gph will top out at 40kts.

I am guessing the 26 with the Napier hull is more of a sharp v and a bit heavier and thus would require more power.

I am not sure how to do an apples to apples conversion to power required for inboard diesels.

[Bruce]

Yanmar changed the ratings by a few HP on most their engine at one time Yannis.

I saw that he purchased a 26 which I've never repowered but wanted to share my experience and his enquiry for the 28 with the lower 4lh.
Parts between those two engines are not interchangeable even though they have the same prefix.

[Yannis]

Bruce, thank you.

I'm glancing through the Yanmar site and see that the 230 is a totally different engine from the 240, and so is the 250!
According to them, the 230 and 250 rev up to 3800rpm, the 240 up to 3300. They also look different.
The 240 is the old 4LHA-STP that I have. Only now it is called 240 and not 240/250...

[DanielM]

Carl, Joel had asked about both the 26 and 28 so I think all the answers benefitted him.

I have always wondered how well 170s would work in one of the smaller Bertrams. It would be interesting if Joef goes that route.

The reason I came across this site (24 years ago - yikes!) was that I had bought a Bertram 25 hull that had the straight inboard version with the Walter v-drives and was looking for info about it, it was my first go at a twin-engine boat. Back then I had heard about the Bertram brand but being a West Texas boy didn’t know much about them.

I got a ton of good advice and Trey (DaJudge) tried to convince me that I should swap the gas engines for Yanmar 170s, turn them around the correct direction and jack shaft them to some newer technology stronger sterndrive legs and have a beast of a B25. I never went that route but I always thought it would have been a cool method.

Joef if you follow the diesel path on the B26 keep us informed, that would be neat to follow. Either way I think you’ll like that boat.

[Joef]

Thanks for all the thoughts. For this season we’re gonna get the other “basics” in order. We’ve redoing the 12v distribution system which has 40 yrs of molestation and corrosion on it- miraculously- even w all the butt connectors and green dust, almost everything worked. Some new modern electronics as well

The crusader 4.3 V6s are gonna stay w us this year. But we continue to think about it. There are still a couple of inboard options for that little boat. Mercruiser makes a 220/250hp 4.5l V6 that might also sit right in there too- we’ll see. It’s a super cool boat- my dad is almost 84. This exact boat was a bucket list thing which adds to the fun.

Will keep you all posted and add some pictures in some other posts

JoeF

[Carl]

JoeF- It sounds like a solid plan to get the basics in order, and use the boat and see the direction it takes you.

Diesel is great, but gas motors do have a place.