A whole new engine

[dieselgrady]

I currently own a 1985 Grady-White Sailfish that was repowered about 9 years ago with a Marinediesel 300HP Hammerhead engine (Supercharged 6.5L). I have been doing my own maintennance and repair, but now it is loosing RPM's and burning oil. (1 pint per hour of operation) I replaced a CDR valve, which is basically a PCV valve, but it didn't help. So with multiple problems , and the cost of diesel mechanics, I'm going back to gas. I was quoted under $10,000 for a new Mercruiser 5.7L that puts out 325hp, which is roughly the same as the diesel. I realize i'll be loosing economy , but diesels are just too costly. The outdrive is a Bravo 3X (diesel) which has a 1:81 ratio. I've been using a set of 22Pitch props and wonder if they will work with my new, higher revving gas engine? This is my first post, and thanks for any info you can supply. One other thought, is it worthwhile going with fresh water cooling? I fish the New York Bight and all salt.

 

[alldodge]

Re: A whole new engine

Since you have one engine and not twins I assume it is the 255, correct?
Boat: 1985 Grady-White Boats 255 Sailfish

While the HP ratings are about the same the torque output of the diesel is much greater. I see you would probably want a big block instead of a small block, a 375HP 496 Mag would be a better choice. The bravo 3X will handle the output of the higher rpm gas engine, weather you would need to change the pitch to achieve optimum performance may be necessary. The ratio should be close enough to work but most gas engines are around the 2:1.

 

[dieselgrady]

Re: A whole new engine

Yes the boat is 25.5'. And thank-you for the speedy comeback, as I'm standing in the cross roads, scratching my head! The larger engine costs almost twice as much, since i'm not in a rush, i'll stick with the 5.7L.. Also it will be a direct fit and no mods will be required. (eliminate diesel fuel return line, clean tank, install bilge blower etc etc.) I have to at least try to keep the price down. And what do you think about fresh water cooling, ? Is it worth it? How long will the manifolds-risers last on the 5.7 without it?

 

[alldodge]

Re: A whole new engine

Yes the boat is 25.5'. And thank-you for the speedy comeback, as I'm standing in the cross roads, scratching my head! The larger engine costs almost twice as much, since i'm not in a rush, i'll stick with the 5.7L.. Also it will be a direct fit and no mods will be required. (eliminate diesel fuel return line, clean tank, install bilge blower etc etc.) I have to at least try to keep the price down. And what do you think about fresh water cooling, ? Is it worth it? How long will the manifolds-risers last on the 5.7 without it?

Salt water cooled engine exhaust and risers last about 5 to 7 years. This can be prolonged if the engine is flushed with fresh water and kept on a trailer. A SB or BB salt will wear them out about the same.

 

[thumpar]

Re: A whole new engine

What about just having the diesel rebuilt? Seems like someone would be able to do it for less than half the price of a new engine and then you don't have to worry about all the changes that need to be made. Those props are not cheap on top of the other stuff.

 

[dieselgrady]

Re: A whole new engine

What about just having the diesel rebuilt? Seems like someone would be able to do it for less than half the price of a new engine and then you don't have to worry about all the changes that need to be made. Those props are not cheap on top of the other stuff.

I had to replace the oil pan a while back and just the labor to pull and replace the engine was about $1200. I would guess at least $12,000 and that's assuming there were no "surprises". The regular yard mechanic labor rate is about $90 per hour and i'll guess a qualified diesel mechanic, familiar with my engine would be at least $125. Diesels have a lot going for them, but they're expensive. And parts for my engine are cheap compared to Volvo-Penta or other high performance diesels. By the way, the boat is docked in Brooklyn,N.Y.

 

[glenn property of pam]

Re: A whole new engine

have you considered at least pressure testing the engine to see whats going on with it. It would be a shame to pull a diesel for a leaking valve seal or something simple. It may be worth asking for a quote for a mobile diesel mechanic to do the test for you as the tester is not as cheap as the one used on gasoline engines.

 

[Bondo]

Re: A whole new engine

have you considered at least pressure testing the engine to see whats going on with it. It would be a shame to pull a diesel for a leaking valve seal or something simple. It may be worth asking for a quote for a mobile diesel mechanic to do the test for you as the tester is not as cheap as the one used on gasoline engines.

Ayuh,.... Agreed,.... Swappin' motors, Without Diagnosin' exactly what's Wrong, is Tossin' out the baby with the bath water,....

A grand or 2 to fix yer motor, sounds better than the numbers yer lookin' to spend,...

Btw,.... Welcome Aboard,....

 

[chriscraft254]

Re: A whole new engine

And if you can't fix your diesel, maybe look into a rebuilt motor instead of a new motor. Is the boat and its age worth it to you to dump 12 grand into it?

 

[dieselgrady]

Re: A whole new engine

Yesterday took the boat for a run and started blowing glycol and overheating. Today replaced impeller, changed oil and took her for a spin. Was hoping to get till the end of the season, but it looks like curtains. Started overheating again and both upper and lower hoses to heat exchanger collapsed. Slowed to idle and cooled off. Looks like there is a leak into the cylinders. No glycol in oil, but there is some pretty bad blow-by (rings are shot) Will try some of that leak sealant and then it's curtains. Just too many bad things (cracked head letting glycol into cylinder, bad blow by etc) I really wood need a complete rebuild, and it's just not worth it. Will try to sell supercharger, manifolds, DB4 injector pump on E-Bay and hope for the best.

 

[glenn property of pam]

Re: A whole new engine

low compression all cylinders then maybe its blow by. Low on one cylinder then maybe a head gasket or cracked head. Theres lots of diesel truck mechanics around my area so getting a diagnosis wouldn't be as hard as where you are. If the engine has sleeves then rebuilding maybe a better option.
There are times when you have truly lost patience with a engine. Then it doesn't matter if the engine can be rebuilt or repaired and I understand that. Theres going to be a lot of steps in changing from diesel to gas including electrical, gauges, etc. Then you will get to the fun part of winter storage and dealing with old gasoline.

 

[dieselgrady]

Re: A whole new engine

I think you are going down the wrong path. You can buy a BRAND NEW 6.5 l. diesel long block for about $5k and it's a plug and play swap. Note, this isn't a rebuilt or a remanufactured engine, it's brand new in the crate.

One example: BRAND NEW 6.5 Longblock Diesel Engine :: SSDiesel Supply :: GM 6.5 TD Specialists

Of course you can do a little shopping and find a remanufactured long block with a warranty for about $3K.

Unfortunately there is a lot more to it than that. Yes you can get a 6.5L for what would amount to chump change, but it would then have to be marinized. First it needs 18:1 pistons, I believe the stock are at least 20:1 and would not last long if supercharged. Then marine injectors, then mechanical injector pump etc etc, cooling via different manifolds etc you get the point. The reason Penninsula and Marinediesel get over 20K is all the additional work and set up. My engine pumps out 300Hp and almost 500 Ftlbs of torque. Maybe that's what killed it? Still, thanks for the thought and i'm all ears! PS I've bought some parts from SSDiesel and they're a good outfit.

 

[thumpar]

Re: A whole new engine

You have all the boltons already. All you need is a long block and switch everything over. Why would it cost more to pull a diesel than a gas motor? ( I know a little more weight but the machine lifting doesn't care.) Maybe it is time to find a different shop or learn to work on it.

 

[glenn property of pam]

Re: A whole new engine

all over the net long block 6.5 with 18:1 marine pistons are priced under 4k (got to love the government surplus flooding the rebuild market). you have the expensive parts already so all you need is a mechanic that's not charging you a arm and a leg to do the swap.

 

[dieselgrady]

Re: A whole new engine

I've done manifolds-risers, injectors,glow plug system, thermostats,heat exchanger, raw water pump rebuild, but switching to 18:1 pistons is beyond my skill sets. The engine cruises 2700-3200 rpm I would guess that would amount to 85-95mph for a regular 6.5L. Most street vehickles turn about 2000-2200 for 65MPH (that's the sweet spot for the engines torque curve) And like someone said earlier, i'm getting tired of tweaking this thing. Like riding my 1966 Norton Atlas, my hands were always greasy and I loved the bike, but I had a lot more time to fish when I didn't own it. And the $1200 to pull and replace the engine? I'm sure it would have been the same for a 7.4L gasser. That's what this thing is about. Sometimes it's just better to start from scratch. I live in the big apple , and diesel mechanics are few and far between.

 

[glenn property of pam]

Re: A whole new engine

I've done manifolds-risers, injectors,glow plug system, thermostats,heat exchanger, raw water pump rebuild, but switching to 18:1 pistons is beyond my skill sets. The engine cruises 2700-3200 rpm I would guess that would amount to 85-95mph for a regular 6.5L. Most street vehickles turn about 2000-2200 for 65MPH (that's the sweet spot for the engines torque curve) And like someone said earlier, i'm getting tired of tweaking this thing. Like riding my 1966 Norton Atlas, my hands were always greasy and I loved the bike, but I had a lot more time to fish when I didn't own it. And the $1200 to pull and replace the engine? I'm sure it would have been the same for a 7.4L gasser. That's what this thing is about. Sometimes it's just better to start from scratch. I live in the big apple , and diesel mechanics are few and far between.

you don't switch the pistons. A short block is the main block including crank, rods, pistons, A long block includes the heads, cam, etc. so everything just bolts on the outside of the block. Talk to any truck driver and they will tell you where to find a diesel mechanic most do not have workshops as they go to the engine rather than dragging the engine back to the shop.

 

[agallant80]

Re: A whole new engine

I wonder if most of the people saying keep your diesel and fix it have never owned on. They cost huge amount of money to repair, just the parts are out of this world. If you have the cash and are willing to fork it over to the yard to go back to gas then go for it. I know peace of mind on the water is worth allot and if you have a headache motor and just want to be done with it I understand that too. I new gas that will give you 3-5 years without any headaches is worth good money. If you spend $12,000 on it and you get 5 years without a headache that is only $2,400 a year. Are you spending about that much right now keeping your Diesel running?

 

[Bondo]

Re: A whole new engine

I've done manifolds-risers, injectors,glow plug system, thermostats,heat exchanger, raw water pump rebuild, but switching to 18:1 pistons is beyond my skill sets. The engine cruises 2700-3200 rpm I would guess that would amount to 85-95mph for a regular 6.5L. Most street vehickles turn about 2000-2200 for 65MPH (that's the sweet spot for the engines torque curve) And like someone said earlier, i'm getting tired of tweaking this thing. Like riding my 1966 Norton Atlas, my hands were always greasy and I loved the bike, but I had a lot more time to fish when I didn't own it. And the $1200 to pull and replace the engine? I'm sure it would have been the same for a 7.4L gasser. That's what this thing is about. Sometimes it's just better to start from scratch. I live in the big apple , and diesel mechanics are few and far between.

Ayuh,.... Sounds like yer mind is made up,....

Whatcha gonna do with the take-out motor,..?? (pm me if yer dumpin' it, I'd Love a diesel motor)

You'll be needin' a Complete Bobtail motor, Fully dressed,...

All ya gotta do is pick which 1,...

Merc,..?? Crusader,..?? probably more, 'n carbed, Efi, Mpi,..??

I donno that the drive gearin' will work either,... maybe different props,..??..

 

[HT32BSX115]

Re: A whole new engine

Ayuh,.... Sounds like yer mind is made up,....

Whatcha gonna do with the take-out motor,..?? (pm me if yer dumpin' it, I'd Love a diesel motor)

You'll be needin' a Complete Bobtail motor, Fully dressed,...

All ya gotta do is pick which 1,...

Merc,..?? Crusader,..?? probably more, 'n carbed, Efi, Mpi,..??

I donno that the drive gearin' will work either,... maybe different props,..??..

Yeah. ME TOO! I'd take it! That 1.81:1 Bravo IIIx WILL NOT WORK with a small block chev engine . You need at least a 2.00:1 or a 2.20:1 drive.

First it needs 18:1 pistons, I believe the stock are at least 20:1 and would not last long if supercharged. Then marine injectors, then mechanical injector pump etc etc, cooling via different manifolds etc you get the point. The reason Penninsula and Marinediesel get over 20K is all the additional work and set up. My engine pumps out 300Hp and almost 500 Ftlbs of torque. Maybe that's what killed it? Still, thanks for the thought and i'm all ears! PS I've bought some parts from SSDiesel and they're a good outfit.

1. Yes you can buy 18:1 short block engines and,

2. YES, 300hp is and has always been a bit too much for a 6.5L diesel......it's ok in a truck that makes 1/4 miles runs......... but put a 16,000 lb trailer behind one and pull Snoqualmie Pass (I-90 Wa State) or The Grapevine (I-5 Bakersfield-LA) every day with that 16,000lb load and they'll break.

They were only designed to produce a max of about 220hp and NOT on a continuous basis........like marine engines.

 

[dieselgrady]

Re: A whole new engine

Good to have so many thoughts on my situation. Agallant80 seems to know where I'm at, but it's hard to give up the smoker. I am still trying to get the season out of the engine. Ran out yesterday at about 2400RPM and as long as I watched the gauges it ran O.K. Also I'm concerned about using the Bravo3X 1:81 ratio. Can't I just prop up? Currently running a 22P. Can the 3x 1:81 to 1 be used on arepower to gas? It seems the further I get into this process the more problems arise. I want to make intelligent choices. Thanks everyone!