Newbie, Yanmars 175 hp. In B31

[Seapalm]

Hello Guys, and thanks for letting me join this fine group, I have been following this site with dreams of owning a Bertram 31. I almost pulled the trigger on a beautiful B28, but the dream would still not be fulfilled. So a 31 it shall be... I'm in the FL Panhandle near Destin and feel fortunate to have dodged both hurricanes so far this year (knock on wood!)...

I own a pair of Yanmar 175hp. engines and ZF drives, and have hopes of installing in my future B31. They have less than 500 hours and are out of a friends 28 Uniflite. That boat is much lighter than the Bertram but not near the hull either, and performed well in his boat. What would I expect in the B31 if it too was lightened up a bit from being renovated, and less weight front the Yanmars? No speed demon I'm sure, but very economical I imagine... any thoughts or experience?
Thanks for your valuable knowledge.

[Tony Meola]

The 170's will be a little light for the 31. I would expect the cruise to be around 17 knots. it will be real stingy on fuel.

I seem to remember reading an article way back when about 31 with the 170's. If I remember how to get to it I will let you know.

[Tony Meola]

https://www.popyachts.com/sport-fishing ... rida-80908

http://www.boats.com/ready-to-switch-fr ... bdHOL4WFpg

Found the article plus one add for one. Looks like you would be able to push the cruise up higher based on what I am reading.

[Seapalm]

Hey Guys, thanks for the feedback, that is a good article and very informative. Those are numbers that I could live with especially considering the cost of other diesels vs the Yanmars.

[1962 31]

i have 210 cummins and cruise at 2200 rpm 20 knots and 2400 22 knots

[mike ohlstein]

What gear ratio are the transmissions?

[DanielM]

I was talking to Cranston today. I know he had 170hp Yanmar's in his Bahia Mar before he had it redone, so I asked him.

He said that he had about a 21 knot cruise with the 170s and 2:1 transmissions. Figured a Fly bridge model would be a little slower. Also he had done work to lighten up his boat. He said it wasn't a speed demon but they were economical to run. Good motors.

[Bruce]

Caveat on those engines. There is a narrow point on those engines where loading won't allow the turbos to spool up thus black smoking.
Used them on a Bert 28 repower.
Ran decent but slow on sea trial. Owner seemed happy. He got dive certified and loaded the boat with 3 guys and gear with full fuel.

Boat wouldn't plane and black smoked. Came by the marina and we off loaded the guys and gear and it was okay.
Owner not happy but he picked the engines. Asked me to convert to 240's. You can't I said.

He sold the boat.

[Yannis]

As Im reading all this, it appears to me that the 31 can achieve better performance than the 28 with a given horsepower.
It also appears that the 31 is more economical to run, at a given speed...(data from the other thread on consumption).
Isnt the 31 heavier? If yes, then could someone explain if the above is true?

And, as Im getting ready to ease my thoughts away, comes the "you cant convert to 240's" !
Perhaps its the air pressure at sea level that hurts me...perhaps I should take the mountains.

[Tony Meola]

Caveat on those engines. There is a narrow point on those engines where loading won't allow the turbos to spool up thus black smoking.
Used them on a Bert 28 repower.
Ran decent but slow on sea trial. Owner seemed happy. He got dive certified and loaded the boat with 3 guys and gear with full fuel.

Boat wouldn't plane and black smoked. Came by the marina and we off loaded the guys and gear and it was okay.
Owner not happy but he picked the engines. Asked me to convert to 240's. You can't I said.

He sold the boat.

Maybe that is why Jim Curly changed them out. I remember when he did that, he was one of the first to go with Yanmars up hear in NJ and everyone talked about it. But he had a car dealership, and access to a lot of this stuff at dealer cost so not so bad for him to do it back then.

[Bruce]

One of the first 31's I did had 170's lag bolted down to the trimmed out plywood covered old stringers when the 6lp came out. The owner complained it was slower than molasses in winter and put the 6lp engines in.

[Carl]

Caveat on those engines. There is a narrow point on those engines where loading won't allow the turbos to spool up thus black smoking.

Bruce, correct me if I'm wrong, wouldn't de-tuning props allow turbos to spool up when loaded heavy?

My thought it's a trade off, go short on power and cruise slow or keep load light to go a bit faster...or overtax motors and be ready to buy new motors sooner then later.

[thuddddddd]

[

Maybe that is why Jim Curly changed them out. I remember when he did that, he was one of the first to go with Yanmars up hear in NJ and everyone talked about it. But he had a car dealership, and access to a lot of this stuff at dealer cost so not so bad for him to do it back then.

Jim Curly?? LOL I guided he and some GM hot shot on a grouse hunt in NH a few years back .. we talked about a lot of things .. boats was not one of them

[Bruce]

Absolutely Carl it will.
In my case the owner didn't want to pay a dive service to change the props on a regular basis. He wanted to fish one week, dive the next, etc. As a new diver he tried changing the props himself underwater, about drowned.

[Tony Meola]

[quote="thuddddddd"
Jim Curly?? LOL I guided he and some GM hot shot on a grouse hunt in NH a few years back .. we talked about a lot of things .. boats was not one of them[/quote]


Maybe he was afraid you would freak out with flash backs of turning a Hatterass into a planter.

[Carl]

Absolutely Carl it will.
In my case the owner didn't want to pay a dive service to change the props on a regular basis. He wanted to fish one week, dive the next, etc. As a new diver he tried changing the props himself underwater, about drowned.

LOL... I know plenty a person that can't change props on land. For our size boats its not so bad in the water, just gotta get timing right or use a tank.

Guess he wasn't content with staying with smaller wheels for fishing and cruising...

[DanielM]

One more caveat. When John had to redo the boat he didn't stay with the 170s he went with 315 Yanmars instead.

I know part of the reason for the 315s was that he found a good deal on some zero hour Yanmars when he was re-doing the boat, but I'm sure the additional power/speed of almost doubling his horsepower didn't hurt.

Additionally he doesn't dive so no worries with all that gear and he put effort into keeping the boat light.

When I was looking at repowering an inboard B25 I had years ago Trey "Da Judge" told me that I should put 170s in that with a jack shaft and stern drives. That actually sounded like a cool option. Maybe you look for a B25 inboard in need of a redo and go that way.

[Seapalm]

Guys, thanks for all of the great replies. All of your knowledge and insight is appreciated and will be put to good use.

I have recently picked up a project B31 and it is now on the hard and being stripped down. This boat has a running pair of Volvo Penta 140 hp desiels, which I plan to sell. It is complete with all the hardware and components, but has been abused and not taken care of. The seller needed to get out of high dock fees and insurance costs so he unloaded it cheap. I also have the Yanmar 170's in mint condition in my barn. I thought about experimenting with making this hull as light as possible, opening up the cabin with only seating, a small counter with a microwave, and a head. The interior sole, hull, flybridge, and front deck are all original. The cockpit sole has been replaced with 3/4" plywood and fiberglass, and is solid.

So how do I shed weight? Bare bones and featherweight the boat without compromising the integrity of the hull and safety. Do the front glass windows add a lot of weight compared to glossing in that area? The front deck, replacing with foam core? Back deck replacing with foam core? Is it possible to make it light enough to run the 170's as they should be ran?

Your thoughts please?

[thuddddddd]

what are the 170's worth on the market? My thought would be that the cost upfront , and long term to lighten the boat and keep it that way as you refine it might be offset .. certainly the lack of "speed" will always be an issue for you and future buyers (in my opinion)

[Seapalm]

Uncle...
I have decided that selling the 170's is the best thing to do. I can recover some costs going forward and let someone restoring a Bertram 25 put these babies in it. They are low hours around or less than 500 and run well with ZF drives. If there is any interest please feel free to contact me. Thanks!

[Tony Meola]

To lighten her up replace as much plywood as you can with coosa board and Azek for areas not structural.

As an example the deck in coosa is half the weight.

Also whatever you do trl and keep heavy objects in genset holding tanks etc. From midship back if possible.

If you do searches you will see batteries placed below the companionway between the engines on a number of rebuilds.

Think weight low, center line of boat and midsip back.

[Goober]

Goober here ; u have some good questions , i have a 78 31 fbc with 170 yan mars with no genset and no extra weight in cabin. We can fish four guys in cockpit and cruise 20/22 knots on the other hand a one cooler trip with the wife will get about 22/24 knots .All of this depends on a very clean bottom !!!! I live 20 miles north of Savannah with the worst salt water , barnacles , slime ; a job in itself. My engines just turned ( knock on wood ) 8000 hrs , are very stingy on fuel ,2.1.mpg . I can't say anything bad about the engines ,but in heavy seas the speed will drop to about 16/17 . If u can stand it the 6 lp engines ( I think 215 or 225 hp ) will be a better setup . Good luck !

[Goober]

What's the price on ur engines ?

[Seapalm]

Palm B
Plan B includes all things Bertram, as I have our B31 started in its restoration project I have decided to look for a more appropriate vessel to install the engines. We will re power the 31 as time and money allows, but recently I have found a Bertram 26 Express needing re-powered, and I feel, a perfect fit for these engines. The boat is everything I am presently looking for to chase Yellowfin through the Winter. I am excited about this project being a short lived re power project and chasing fin and tail in the very near future. So the Yanmars are staying home, but I thank everyone for your knowledge and support! You folks have been great!