What is/would be your engine of choice in a 37 to mid 40s Cruiser

M

mrsrobinson

Well-Known Member
Mar 9, 2006
7,704
Virginia
Boat Info
2001 380DA
Engines
Caterpillar 3126
I have a read a lot on diesels, I know the pros and cons, gas engines as well. Assuming all else equal, what engine (make and model) would you chose, and why, for a 37' - 40' Cruiser style boat?

Remember, "all else equal". No "well that depends on.." ;-)

Ok, since I know it's going to go down rabbit holes, assume river boating, overnight anchoring, weekend trips to other marinas, maybe an occasional 8-10 hour cruise, brackish water. Let's say 40 - 50 hours of use a year. early to mid 2000s boat.

Gas seems to be the Merc/Volvo 8.1s. Diesel seems to be Yanmar 6LPA-STP, CAT 3116/3126 and Cummins. I grew up around Caterpillars (heavy equipment construction) and my GFs brother-in-law used to turn wrenches for them and is now in sales for them, so I tend to like them better. I have no experience with Yanmar or Cummins though.
 
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Gas 8.1s. I have a 37' with gas 5.7s and wish it was offered with 8.1s. For the price to drop a new one in compared to a diesel, you can buy a lot of fuel. Easy to wrench on, fairly cheap to repair - how do you go wrong with the 8.1?

And, I'm a Lake Michigan boater. So she's ran 40-50 hours a season, out every winter as well as a few longer trips every year. I haven't wished for a diesel yet...
 
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I've had big block v8 experience and now have diesels. No question in my mind diesels for that size boat. Diesels can propel a boat at significantly lower rpm than big block gas engines. An internal combustion/diesel engine can be viewed as a fuel and air pump. The more it spins the more air and fuel it sucks in.

Yes, I realize at 40-50 hours a season fuel economy can take a back seat. But it may not to a future buyer.
 
There's a HUGE difference in vessel size from 37' to mid 40's. I don't think this survey will be particularly useful with that much range :)

The usefulness of gas engines becomes less and less debatable as you get into that magical 40' range. By the time you're at 45' I don't even think it's a discussion anymore...'cause they don't offer gas?

And for all the diesel purists, good luck finding a 37' boat with diesels. Those buggers are unicorns...
 
Stee6043 said:
There's a HUGE difference in vessel size from 37' to mid 40's. I don't think this survey will be particularly useful with that much range :)

The usefulness of gas engines becomes less and less debatable as you get into that magical 40' range. By the time you're at 45' I don't even think it's a discussion anymore...'cause they don't offer gas?

And for all the diesel purists, good luck finding a 37' boat with diesels. Those buggers are unicorns...
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I have a friend with a 40' Sedan Bridge and he's got gassers in his, no complaints from him on performance. I agree though, 45' is likely the threshold that gas is no longer an option.

I'm happy with my unicorn, I wasn't sure about going diesel when I purchased, but I'm very happy with them so far. While I was searching for this exact model, I would say it was 50/50 on the boats I found whether they were gas or diesel. If you do any amount of longer range cruising, diesel makes sense. The use case that the OP has would probably dictate gas for me.

The other thing to consider is generator usage, not sure if there's much difference in the GPH for gas vs. diesel gensets, but diesels are made to run for long periods of time without issue, not sure that the same can be said of gas.
 
A 3200, 3500 or 4200 Tiara Open with Cummins. Each boat is 37 feet long or longer and Cummins has strong service support in West Michigan. Each of these boats handles big water well and is very comfortable for two people to live on for a week to a month.
 
Ok, 37' to 40' Which engine (make and model)?

I was all set to go with the Merc 8.1s, now though, thinking this "could" be the last boat I am curious about diesels. Every Merc 8.1 I have been on/surveyed/sea trial had a fuel and/or compression and/or electronics issue. At the end of the day, by the time you throw $$$ at the big blocks to keep them running, perhaps it does equal out to go with diesels for the pros.
 
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Pirate Lady said:
So you’re planning on using it about 5 times a year? Get gas, you wont need diesel with that use.
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No, during the boating season we'd probably use it at a minimum every other weekend.

I didn't mean for this to be a gas versus diesel pros and cons which should I get thread. More if you had to pick one engine/make/model, which one would it be, and why. More of a curiosity question.
 
One should also consider the weight of the boat. I had a 390MY with the 8.1s and it was under powered without a doubt. The other thing is on how you intend to use the boat. We boat, meaning a 80-100 mile run frequently. If your on a lake and 3-4 miles and drop anchor gas is fine. I am a diesel guy in larger boats. Hands down, they are more reliable and efficient it.
 
How long do you plan to keep the boat? Bigger later?
If this is a 3 to 5 year boat then diesel will be overall more cost effective and end up an easier sale in the end.
Remember higher cost going in and higher sales going out for the diesel. Everyone seems to forget that salient point.
I had a 2000 400DA with the Cat's and I loved that boat; loved everything except for the canvas top.
So, I'd move up to a 410DA or 42DA with the hard top; seems like a lot of people really like them.
 
mrsrobinson said:
I have a read a lot on diesels, I know the pros and cons, gas engines as well. Assuming all else equal, what engine (make and model) would you chose, and why, for a 37' - 40' Cruiser style boat?

Remember, "all else equal". No "well that depends on.." ;-)

Ok, since I know it's going to go down rabbit holes, assume river boating, overnight anchoring, weekend trips to other marinas, maybe an occasional 8-10 hour cruise, brackish water. Let's say 40 - 50 hours of use a year. early to mid 2000s boat.

Gas seems to be the Merc/Volvo 8.1s. Diesel seems to be Yanmar 6LPA-STP, CAT 3116/3126 and Cummins. I grew up around Caterpillars (heavy equipment construction) and my GFs brother-in-law used to turn wrenches for them and is now in sales for them, so I tend to like them better. I have no experience with Yanmar or Cummins though.
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So to answer your question, picking one and why, I would go with a Cummins 6CTA. At 430hp they have more than enough power to get a mid 40s boat going at a good 20 knot+ cruising speed. I also like the availability of parts and good mechanics in the early to mid 2000 vintage boats. My second choice would be Cats for many of the same reasons. The only reason I put the Cats second is due to some of the soft block issues with the 3116/3126 that for the most part have been resolved.
 
Shoyrtt said:
So to answer your question, picking one and why, I would go with a Cummins 6CTA. At 430hp they have more than enough power to get a mid 40s boat going at a good 20 knot+ cruising speed. I also like the availability of parts and good mechanics in the early to mid 2000 vintage boats. My second choice would be Cats for many of the same reasons. The only reason I put the Cats second is due to some of the soft block issues with the 3116/3126 that for the most part have been resolved.
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All resolved; I believe all of the French blocks have been accounted for as well as the valve issue. The only thing I saw and saw on a post here about a month ago was a Cat 3116 with the stainless steel riser - I thought all of those were gone also.
 
Golfman25 said:
How do maintenance costs compare?
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Between boats or between engines?
If engines, diesel annual maintenance obviously would be a bit more if done per the book but not enough to elicit a determination between the two. Let's say you have a company do all of the service, so we have apples to apples. And let's say we are comparing 8.1 gasoline engines to Cat 3116 diesel engines: a fair comparison, right? In reality for annual maintenance, per the book, is probably a couple of hundred dollars difference. For the periodic maintenance like cooler cleaning, exhaust riser replacements, ignition parts, impellers, coolant, valve lash, etc - I don't think there is a difference. The gasoline engines suffer more down time and repair costs simply due to the complexity they exhibit. The big benefit and what drives the additional purchase cost of the diesel boats is the durability, reliability, simplicity, and longevity of the engine which is far more than the gasoline counterpart. I think I had a tick over 5000 hours on my Cat 3116's on my last boat and those engines still had all of the original parts on them sans air filters and rebuilt turbos and they surveyed out in excellent condition when I sold the boat; it would be a rarity to see that in the 8.1's. That is why one buys and sells diesel boats for more.
 
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All else equal? I'd go with the better maintained boat. Above 40' diesels (but MX is a major consideration). Cummins or CAT? Both are excellent power packages and I don't think you could go wrong either way.

As far as maintenance, CATs have been easier than the last gas boat I owned. Getting to the spark plugs for changing was damn near impossible. The few parts I need I can find and order easily online and have shipped to me from the local CAT dealer.

For annual MX, you will have more cost due to larger amounts of oil/fluids. For a CAT 3126, I usually buy 15 gallons of oil and 4 gallons of ATF for the transmissions, so about $400 in oil/ATF. The only other items are CAT Fuel and Oil filters at $15-$20 each call it $100 for both engines, and 3 new Racor filters (including the generator) at about $50. So $550.
 
My rule has always been 40 or less for express boats = gas and warrent a good sea trail. Bridge boats need diesel to perform adequate imo. I've been on plenty of SRs 37-40 with 8.1s and always thought they did ok.only exception is long range cruising.
 
mrsrobinson said:
Ok, 37' to 40' Which engine (make and model)?

I was all set to go with the Merc 8.1s, now though, thinking this "could" be the last boat I am curious about diesels. Every Merc 8.1 I have been on/surveyed/sea trial had a fuel and/or compression and/or electronics issue. At the end of the day, by the time you throw $$$ at the big blocks to keep them running, perhaps it does equal out to go with diesels for the pros.
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You must have bad luck with engines! When shopping for both of my Sea Ray's the 7.4's were all bullet proof. With a compression test and sea trial it was about the only thing I never worried about. Wet decks and generators that didn't run were my most common challenges...
 
I'll throw this out there, diesel boats are safer. Diesel will burn, but won't explode like a gas boat. And if you want to sleep on the hook with the generator running, you'll sleep better with a diesel generator running vs gas.

Of course, maintenance and prudence do come into play. just sayin......
 
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