Boat Engine Options

[TORQUE THIS]

I am looking at a new boat. It's a 19' cuddy.



It comes standard with a Mercruiser 4. 3 V-6 190 HP.

An option is a 1. 7 Mercruiser diesel rated at 120 HP.



Will there be a big difference in top speed???

 

[midlife crisis]

TT- if there was any other diesel option on the table, I would tell ya to go for it. The little merc diesel has a checkered past, and its history has shown it tolerates no overloading or extended high rpm use. Other (reputable) feedback is a tendancy to crack pistons at the wrist pin bore. All may be well at test time, but throw on 2 buddy's, beer, bait & babes and well that poor little thing will have its tongue hanging out. Forget trying to pull a skier or tube- you will wish you had the gasser. My . 02-

 

[TORQUE THIS]

Huh, just doing some research and find out that it is a Cummins 1. 7...





I use the boat mainly for relaxing, with the family... occasional tubing, no skiing...

 

[GFritsch]

Sometimes Diesel is not available at the lakes around here. I would be very tempted though. Is it extra cost with the Cummins?



Top speed could be higher with the right prop.

 

[Hohn]

IF I remember, all Mercruiser diesels are Cummins.



I hate to say it, but I'd go with the gasser on this one. Diesels are great, but not really applicable to a pleasure boat.



If you just plan on tooling around and are happy with a max speed of 20-25 kts, then the diesel might be a good option.



IMHO, you'll never regret getting the biggest engine you can on your boat.



jlh

 

[Brand-X]

Though this seems cool to us who live to breath diesel fumes, if you ever wish to up grade to a larger boat the diesel engine in a small boat could make it hard to sell... . George

 

[midlife crisis]

"Top speed could be higher with the right prop". Sorry to disagree, but you never prop for speed. Not if you want the engine to live. You prop for the engine's for the correct rated speed, not the boats.

 

[GFritsch]

MC - Interesting, I am not an expert on props. I have a 98 Mastercraft 190 with the LT1 engine. It pulls very quickly to redline (about 52mph) Talking with I guy at the lake who had a very similar boat he said he got 60mph with a different pitch prop. The water would have too be pretty calm to go that fast.



Could have just been the beers talking---

 

[midlife crisis]

Same for same, 8mph might be a bit much. Certainly different boat speeds can be obtained thru propping, however, engine loading beyond its design will be caused. Your example features 2 different boats, I assume on 2 different days, and again assuming, 2 different speed indicators (and 2 operators w/ 1 exhibiting beer muscles). When comparing boat speeds, we always try to eliminate as many of these variables as possible, even accounting for current and wind. A gas engines maximum rpm is usually given a range- with the desired being at the low end fully loaded (ie people,fuel,gear,dirty bottom & filters). As compared to perfect conditions-(light load, tuned up, clean bottom) reaching its max. An example is the 4. 3 V-6 G. M based engine from the orig post. This engines rated rpm from a manufacturer that I am familiar with is 4400-4600. This means on test day, hopefully, the boat manufacturer is following the engine manufacturers guidlines, and propping to 4600. Sure, a bigger prop will gain some speed to a point, but as rpm drops off with prop increase, it will reach a point, and then start going slower. Throw in the load factor ( boats get heavier, not lighter), and now cylinder (peak) pressures and temps are higher then designed. This is one reason why the diesel engine manufacturers typically do not give a range, but a bottom line figure for a fully loaded boat. This is regardless to where the engine is run, if its overloaded, its overloaded thruout its entire rpm range. I disagree with the diesel "not really applicable to pleasure boat" "only in the 20-25 kt range" comment as well. The Yanmar/ Mercruiser package as well as larger Cummins/Mercruiser package in a given boat all exceed these numbers, as well as the package that started it 20 years ago, the Volvo Duoprop. The Volvo in current form has props available that will push a given hull to 45+ knots. My . 03-

 

[HoleshotHolset]

Mark - it all depends on who you talk to... BUT, even the 4. 3L has a troubled past.



Straight6Jeff ate at least 2 of them... I ate one in my old truck... and there wasn't a single time when I was in the GM dealerships when they weren't swapping out a 4. 3L...



The new GM midsize trucks and SUV's are running I-5's or I-6's... to get away from the 4. 3L.



I've always been a huge fan of the 4. 3L, though... . I loved mine until it ate itself.



Dad used to have a 19' Four Winns with the 4. 3L - we never had an ounce of trouble out of it. Marine versions of engines are usually balanced quite well and have beefier parts - so maybe we should have less reasons to hate the marine 4. 3L...



Find out more about that little diesel - it certainly sounds interesting. I'd imagine it's quite a bit more $$ compared to the gasser, though...



Matt

 

[TORQUE THIS]

The boat w/ the gasser is around 25K, w/ the diesel it is only 27K.



www.stingrayboats.com



Looking at the 190 cuddy.

 

[HoleshotHolset]

Looks like it'll go 42mph with the diesel - 500 pounds of people and 200 pounds of gear... I don't remember which prop I chose...



Here's a link to the Cummins/MerCruiser (joint venture) .pdf that gives a brief description about the little 1. 7L Cummins



It has mechanical injection - which is always a good thing. I'm going to see if I can find some more info on that little Cummins.



Even without doing much research - I'd go for it if I were you - it's only $2K more... not a big deal at all.



Matt



On edit: Found more info... here.



"The 1. 7-litre, 120-horsepower, diesel is a product originally made for Japanese company Isuzu Motors Ltd. at Isuzu Motors Polska, sp. Zo o. (ISPOL) in Poland.



Mercury Marine said that the ISPOL factory is one of the fastest-growing engine producers in Europe.



The engine began life as an automotive product, said Karuhiko Kurokawa, general manager of Isuzu Motors Powertrain Sales.

Mercury claims that the engine is 25 percent lighter than others in its class.



It features a direct-injected, turbocharged and intercooled, four-valve, double overhead cam design, producing maximum horsepower at 4400 rpm. "



Very interesting... it's not even a Cummins at all.

 

[RT66DOC]

Having had both, I vote for:

Big boats - Diesel

Little boats - Gas

BTW, diesel boats don't seem to blow up as much as gas boats.

My . 02

 

[TORQUE THIS]

Matt, why is it listed on the Mercruiser/Cummins Marine site...



Cummins would advertise an Isuzu diesel???



Did you see that cruising speed burns 2 GPH!!!

 

[HoleshotHolset]

The MerCruiser/Cummins joint venture is packaging it and marketing it... Cummins isn't building them.



Cummins doesn't make a 1. 7L, DOHC 16-valve, diesel - so they're marketing someone else's engine...



I didn't notice the fuel consumption figures... that sounds awefully low @ 2GPH...



Matt

 

[HoleshotHolset]

I'm seeing 7. 1GPH on page 13 of this .pdf...



Matt

 

[TORQUE THIS]

That at WOT... Cruising speed is around 2200... 3 GPH... HAPPY NOW!!!

 

[HoleshotHolset]

Oh - I thought throttles only had two positions... idle and WOT. My bad.



3GPH at 2200rpm is pretty darn good... . very good, actually.



Matt