New owner

[Dominion]

I recently purchased 1989 41 sport fish model. 550hp 692's, looking for honest speed from others, as this boat was lost in time for twelve years. The inside looks exceptional, outside ,as one would expect cleaned-up but ready for paint. Very strong built boat and looking forward to it. I was able to get 17knts at 1800, no smoke, 2150 rpms, with scuba cleaned bottom. Thanks for any guidance.

 

[Phasma2128]

17 knts sounds just about right. My 1994 48cpmy with 6V92’s runs out about 17 knts. If you’d like another possible knot or two you could have the props scanned to determine if they are perfectly tuned. I wouldn’t think that would be mandatory but it would tell you if the props are functioning at peak levels.

 

[madhatter1]

If your max RPM's are 2150 you are missing 200 RPM. Could be overprop or gov setting. Get a true Detroit Diesel 2 stroke guy to performance test the boat and check your gauges against actual RPM's and temps. I suggest a full service to the cooling system including new coolant as this is critical on the 92 series.

 

[jim rosenthal]

It sounds a bit low to me, and it appears you aren't getting rated revs as noted above. I agree, get the engines checked out, and scan the wheels. I think those were 20 knot boats WOT when new.

 

[Bob Bradley]

I agree that, presuming the engines' racks are set properly, fuel and air is not restricted in any significant way, and the hull is fairly clean, then you are probably over propped.

That said, don't hesitate to dig deeper. I spent a good deal of time and effort trying to find a missing couple of hundred rpm on my kids 37C with 671ti engines. Props are 23 x 22 and we were preparing to have them detuned somewhat. Then we found the spare props under the vberth already 23 x 19, fresh from the prop shop. We figured that was probably the answer, but I wasn't convinced and kept digging. I got my hands on the original engine spec sheet from J&T and discovered that the injectors were wrong. Original specs called for M95 injectors, but N90s were in the motor. My guess is that the PO was trying to detune the engines, lost his top end rpm, and chased his loss by further detuning the props.

We will be replacing the injectors in the spring and not swapping the props until we see the results.

My point is, be absolutely sure your engines are running properly before you mess with the props. That should be your last step

 

[Captain Ralph]

I agree that, presuming the engines' racks are set properly, fuel and air is not restricted in any significant way, and the hull is fairly clean, then you are probably over propped.

I got my hands on the original engine spec sheet from J&T and discovered that the injectors were wrong. Original specs called for M95 injectors, but N90s were in the motor. My guess is that the PO was trying to detune the engines, lost his top end rpm, and chased his loss by further detuning the props.
We will be replacing the injectors in the spring and not swapping the props until we see the results.

Good find on the injectors.
Big difference from M95 to N90 injectors. Including the price.
I hope no other mods were made in those engines (turbos?)

 

[Tinker]

Sam’s brochure claims 6-71 TA 450 horsepower will do 30 knots plus but I might have picked the wrong model brochure and we all know salesmen. I saw old video of JP Frog doing 27 knots with 550 692 in heavier 45 Hatteras. For what it is worth.

 

[madhatter1]

I would think in comparison to my 650 HP 46 it should be nearly the same. A few feet shorter, lighter, and just 100HP less per side. Not sure about 89 hull design but both my 34 and 46 hit a wall at 30-31 MPH and don’t want to go much much faster even when you have throttle left. But below that should be performing nicely. Take Bob Bradley’s advice and check everything. Something is amiss. The good news is it looks like you have untapped potential!

 

[madhatter1]

Sam’s brochure claims 6-71 TA 450 horsepower will do 30 knots plus but I might have picked the wrong model brochure and we all know salesmen. I saw old video of JP Frog doing 27 knots with 550 692 in heavier 45 Hatteras. For what it is worth.

27 knots is 31 MPH, right where the imaginary wall is.

 

[Bob Bradley]

Good find on the injectors.
Big difference from M95 to N90 injectors. Including the price.
I hope no other mods were made in those engines (turbos?)

I hope not, and kinda doubt it. That would have been a pretty big expense, just to make an engine run slower. 10 years ago, it seemed that everyone was praying at the detune altar trying to get more longevity out of their engines, and I'm guessing this may have been the incentive. Or, as you mentioned, maybe just trying to save a couple bucks on injectors or had a faulty mechanic. I doubt we'll ever really know, as the PO (Hcalmar from this site) is, unfortunately, deceased, and we haven't found any documentation indicating their intent.

 

[Dominion]

Thanks to all, I have what some say is a real Detroit mechanic coming down to inspect, Tommy S, from Western Branch back in the day. I like those performance numbers you guys are giving , but they sound somewhat speedy? I'm thinking complete rebuilds with me doing tear down or Cummins 600HP. My question here is has any body else done this and if so, did the 692's come out the door or the future salon sun-roof? I am handy with boat work, but experience toward this is appreciated. The engines did sit for ten years!

 

[jim rosenthal]

If I were repowering that boat, I would buy Cummins M11s from the reman program at Cummins. I would buy them from T&S Marine in Crisfield, MD.

But why don't you get some seat time with her and sort out the issue of the missing rpms, first, and see how you like her with her original engines? I'm all in favor of modern engines, but you might not need to repower. Save yourself 150k at least and just go boating.

 

[SEVEN]

Take care of her.

 

[SKYCHENEY]

If I were repowering that boat, I would buy Cummins M11s from the reman program at Cummins. I would buy them from T&S Marine in Crisfield, MD.

But why don't you get some seat time with her and sort out the issue of the missing rpms, first, and see how you like her with her original engines? I'm all in favor of modern engines, but you might not need to repower. Save yourself 150k at least and just go boating.

$150k???? Ha. That's just for the M11's. No gears, no labor or other parts. Try $250k++

Inflation isn't just in groceries

 

[jim rosenthal]

Right, it's been a while since I bought engines, and I hope I don't have to do it again.

 

[Dominion]

Thanks again! The conservative approach to waiting and seeing after complete qualified inspection is warranted. I will keep posted, as my last boat had Stewart Stevens 892's and I had good fortune.I very much appreciate the input.I think you are right and I may have found a diamond in the rough.Just need to paint and enjoy!Hope you guys don't mind, but in the continuing process I may have more questions? Thanks again.

 

[jim rosenthal]

That's what this forum is for. Congrats and happy holidays.

 

[Dominion]

I don't mind, kinda anticipated it! I have water ,don't know if salt or coolant, coming off top of cylinder, in govenor housing,under valve cover, in airsep pressure release hose, valves are leaking fuel on stand on side and pour fuel in test ! my interest is to know why? I really didn't see water coming from around cylinders inspection cov, Cylinder O-rings. I did pressurize expansion tank up to 15lbs and then turned 6v92 TA over couple times with shut-off depressed, as I thought maybe water pump was leaking when rotating, as I couldn't get pressure drop while sitting still. I was getting quite a bit of water in oil after letting engine idle and then set over night.Looking for experience of this, potential cause? After- Cooler? and yes, one head is off now, nothing glaring to novice eye, o-rings looked good.I did not run the engine, as I thought something was wrong when I looked at coolant and it had what appeared to be soot floating, so I started scratching the what is it? I anticipate the rebuild, but would like to know why? Remember I bought boat after she had been sitting for no less than ten years without running, but was kept cleanand no I didn't get engine survey, as again anticipated rebuild on both.

 

[Dominion]

I did not run the engine above idle!

 

[rsmith]

Thanks to all, I have what some say is a real Detroit mechanic coming down to inspect, Tommy S, from Western Branch back in the day. I like those performance numbers you guys are giving , but they sound somewhat speedy? I'm thinking complete rebuilds with me doing tear down or Cummins 600HP. My question here is has any body else done this and if so, did the 692's come out the door or the future salon sun-roof? I am handy with boat work, but experience toward this is appreciated. The engines did sit for ten years!

Tommy Shook?