Questions about upgrade from a GT150 - what to expect

[greglenz]

I have a '85 GT150. Pushes my '92 DynaTrak Fish & Ski without any problems and can run about 52 or so. It gets +/- 2 miles to the gallon on the water. Running a 22 Raker.

At some point I would like to upgrade and always have my eyes open for a replacement outboard. 150HP is the stated capacity of the hull. I would like a little more speed and a more importantly better gas mileage. I also long for a smoother running machine especially thru the no wake zones.

Is an "Eagle" outboard (150 Fast Strike or Intruder) a good upgrade given my goals or do I need to go to a DFI?

Will my controls need to be replaced or can I swap them the new outboard?

I cannot aford new and would have a hard time justifying the cost at least on this hull. So unless something crazy happens I will be buying used.

Thanks,
Greg

[Neveredge]

The fast strikes are good outboards but they won't be any faster than what you have now. In fact your crossflow 150 probably makes more torque than the fast strikes do.

The early fast strike 150s made real good power but most of them recieved a recall update that was designed to slow them down. OMC denied this but that is what it did. If you can find a 91 that hasn't had the recal done you would be in great shape.

A 2001 or newer 150 ficht would be a great motor for your boat. It would really increase your fuel econmy and it would run close to what your GT does.

The best way to go is to just get a new 150 HO etec. Of course thats a bundle of money.

There is a guy on screamandfly who has a set of early 150 heads that have been shaved for sale. These would give you more punch and a little better fuel economy.

If your interested I'll find his number.

[302w]

If you are able to ship the motor, I would let Fred on here freshen it up with a light hone and new pistons and rings.

[greglenz]

So I am getting the impression that it may not be cost effective to replace this outboard.

Moving to a worst case scenario if this outboard were to "let go" would I be better off rebuilding it or buying a used newer model?

Also what would it cost(approximately) to "freshen this thing up." I am pretty mechanically inclinded is this something I can handle myself with the help of machine shop. I suspect if I freshen it up, then i can help to insure that it keep running for a few more years?

Thanks,
Greg

ps Neveredge, any idea how much for the heads?

[ChampioNman]

I've got a set of 2.6 heads and a bubble back but won't do you much good unless you open up the exhaust. you can't make it if you can't push it out. On a FnS Ebbtide even if you make the mods, you'll have to run at least 93 octane. That is why we don't recommend mods here. your best bet is if you need to is to freshen up the motor. NE and I can help you out on some minor mods to your GT (I love 'em) but I won't put them up here. On your age hull the extra weight of a DI/E-tec may cause some transom problems due to the added weight. They are heavier. Parts are still available and they are good motors.
If you can find a Silver Strike series Eagle motor then you would see an upgrade in performance but they are few and far between. They made Merc cry foul back in the old OMC boat racing days.

Yes the controls and cables will work on a swap out.

[302w]

Assuming that the motor is in good shape, I would keep it and freshen it up but that's my opinion. If you are mechanically inclined then I say go for it!! Just make sure you have a good manual. Off the to of my head I would think you could rebuild it yourself just under $1000 but don't quote me on that.

[greglenz]

Championman,

You hit the nail on the head about the high octane - gas is high enough without having to run premium, so I don't have any desire to go radical. I may hit you up later for some low tech mods, but before I do that I want to make sure that I am starting with a good foundation.

How do I determine if it needs to be freshened up? I suspect that this is first thing to check. When i bought it a couple years ago it had about 85+ PSI on all the cylinders. This was checked with the engine cold. What is the desirable compression for an '85? And what is the proper way to check the compression (warm - cold - throttle open closed)

What else determines that the engine is in good shape as 302w stated in his post above? This thing starts easy everytime. Runs good once warmed up (cold blooded little devil.)

I am guessing I need to replace some bushings in the trim cylinders and needed to clean the tilt/trim systerm check valves. Also needs new new motor mounts, but otherwise I think it is solid.
Thanks,
Greg

[ChampioNman]

After 20 years of running hard, that is a tribute to any motor. I take the readings both ways cold and at temp to compare them. 10% overall variance is OK. A thorough decarb will help some but after this long a tear down is in order. You can get a manual from http://www.kencook.com. You can check the part numbers at the parts link at the top and call your local BRP dealer or the parts chick at Riverside Marine for prices and make your decision. You'll need a gasket set and a bunch of other stuff so $1K won't be far off with your labor. Normal shops charge about $2.5K for a rebuild.

[greglenz]

This engine was rebuilt approx 8 years ago by the previous owner. The crank broke. I guess, I do not know for sure whether he put on a new powerhead or rebuilt the original, but I got the impression he had it rebuilt.

That made me wonder: If it has been bored once can it even be rebuilt. I saw on the parts pages that you can get STD pistons or .030 pistons. If it is already .030 can it be re-sleeved?

Given that it has been rebuilt once a teardown may or may not be in order. I know that if the compression is more than 10% variance between cylinders, it is time to freshen this pup. However is there a minimum PSI that I should expect, or should it be based solely on the 10% rule of thumb? I have come to understand that this era was a low compression block anyway?

Also I just want to clarify - based on previous post regarding this subject that a eagle based outboard would not offer any more performance, but would it offer any better fuel economy?




Modified by greglenz at 10:53 PM 2/8/2006

[302w]

I'm not going to speak for Fred because I couldn't hold a candle to Fred's experience but your motor should be rebuildable. My 115 blew up once about 11 years ago and had it rebuilt by "good mechanic" (bored out.030) then it blew up again about 7 years ago. Last august my friend and I rebuilt it (.044) and put oversized pistons in it and took the oil injection off.

[Neveredge]

An eagle would provide slightly better fuel economy but it won't be all that noticable. You need to go to the DFIs to notice the difference.

You said you wanted to run on reg. pump gas, that leaves out ALL performance mods. The very first thing you do to increase performance is to up the compression which means high test gas.

All other mods would be internal as there really aren't any bolt on mods that actually work. Besides heads of course. And going internal without compression will KILL your hole shot.

If it were my motor I would have it rebuilt by a reputable shop and leave it stock.

You can get pistons for it up to .060 over. Weiseco makes them.

As for compression on an 85 150 I believe you should be at about 115 psi. But all compression testers and procedures are not equal so your motor may be just fine.

[Bassmeister]

Shawn and Fred have given you the good scoop! Rebuild her and ride,ride, ride!!!!!

[THE WITCHDOCTOR]

Your mota is a low compression motor, 85-95 is what they should be... I would go back stock and run it forever...