Advice on pre-purchase used boat motor compression test

[Rhangrea]

I am in a process of buying a used boat and during motor inspection compression came out as below. Twin engine 1998 Yamaha 150 HP Ox66
Port: 115, 125, 105, 120, 100, 115
Stbd: 110, 112, 100, 115, 95, 100

The mechanic (Yamaha mechanic from sellers marine shop) says motors are OK. When I asked him about conventional information that all compression should be within 10%, he says Yamaha doesn't have factory spec like that and with use of Ring Free it is OK. He didn't include hour usage in the inspection.
Seller bought the boat 18 months ago and have done some work on it.
Nov 07- Port motor hard to start with kill lanyard not attached, grey wire comming out of strbrd motor L.U. and both motors leaking trim fluids. Replaced trim rams and tilt ram seals, port primer pump replaced with primer bulb.
Jan 08- Strbrd throttle hard to shift and both motors squeal loud when its down and hit the ram. Removed lower unit freed & greased shift control. Replaced drive support bushing to fix binding & check throttle.
Jun 08- Annual service & check trim system. LU oil, grease, impellers, plugs, thermostats, fuel/water separator, test run, check idle, , replace port trim seal, check fluid on strbrd.
Aug 08- Strbrd motor stalls during long idle intermittenly. Intermittent high fuel consumption (14gph normal but 22gph once). Fuel pump diaphram leak and found debris in one of the carbs idle jet. Set sync and link and test run.

What do you guys think? Would you buy it or what? How much would it cost to rebuild power head? Boat is little rough but has exactly the set up I am looking for. 1998 Grady White Gulfstream.
Thanks for your advices in advance.
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[striped bass]

The motors have seen better days. You will have similar maintenance headaches with these motors. Move on to another opportunity.

 

[sickday]

I voted "pass"unless you can negotiate a full service. Unless the price is already discounted?

 

[Seahunter]

Not sure I'd walk away from a boat that was what I wanted becouse of something held on by 4 bolts.

If you like the boat, buy it under the premise that you'll have to repower, sooner or later and make an offer accordingly.

My “needs repowered” is going on 5 years of service.

 

[BobP]

1. Figure the value of the motors at no more than $1K each, basically, the value of the prop'd lower units.

2. Don't figure you will be served by these motors too long. Misfiring on the idle and troll, fouled plugs, etc.
Be prepared to spend $30K on reporwering. Used twins are not readily found, and what dealer has available is double street value, you may end up buying an entire boat to get used motors.

So you are buying the boat, motors are freebes.
This can be a good deal for someone who has newer motors from an old boat who is keeping them.

 

[Grog]

Are these motors carbs or injected (OX-66's). From the mech's list it sounsd like the motors have carbs. It looks like the motors will need to have ALL the carbs rebuilt. The popping and stalling at idle is probably a gummed up carb, and the high oil cunsumption is probably from the oil rod not being set properly. As as compression, some models have different compression ratios for certain cyllenders. I don't really like those numbers but if the boat is "rough" odds are you have a decent amount of carbon in there (lack of ringfree). If the motors are a real paing to start when cold, the carbs most likely need work.

Oh, and chage the fuel pumps and the oil in all 4 tanks, and a good seafoam treatment.

These are the best situations for the motors. They will probably last a while but don't be suprised if they turn into maintenance nightmares. If you're handy, you can do just about all the work yourself. Give a lowball offer, there can be a long laundry list with this boat (turst me) if you really want this boat. You have the upper hand being the buyer in this market, be sure THIS is the boat you want.

 

[gradyfish22]

If your planning to use the boat as is, I'd walk away, if the deal is right and you are getting a good deal and are ok putting some bucks into it to rebuild the motor it could still be a good deal, but be aware it will need some work. It is possible it could be something that can be fixed without a rebuild, but if it is not attended to it will become a rebuild situation. 10% is typically the limit everyone states for engine compression variance, but what is the difference between 10 and 11%, not much. More importantly this is just showing you something is going on in some of those cylinders that needs attention before the engine does fail on you. If the boat is competively priced with other's, more on to one without problems, if the boat is the one you want and the price is a great deal, and with the added cost of the work will put it below or at sompetative pricing, it would still be worth considering, plus if you do rebuild it you know the engine should be in good shape for a while to come, where even an engine that checks out today might have issues in a year or so, something a rebuild shouldn't have, yet that isn't fool proof either.

 

[plymouthgrady]

I would pass, no question. 105-125 is too much of a PSI difference. there are too many boats in this market to take the financial risk. It would be one thing if the boat was filthy, you can look past that in your offer but the engines are the life of your boat.

 

[Tashmoo]

Too much spread in the compression numbers for my taste from high to low you have a 28% spread. I also believe the mechanic is wrong, Yamaha does provide a spread range on compression if I remember correctly the top and bottom end for my old 200 hp two stroke was 130 - 115 PSI. Look into it more and if there is a published spread disregard your mechanics input as you have just proved his input is not trust worthy.

From the issues you describe these engines clearly have not been well attended to so as Bob P said figure them to be worth essentially scrap value. If the deal works on that basis push forward if not walk. There are plenty of well maintained good boats out there.

 

[Rhangrea]

See the photos below.

The asking price was $23k and the price is firm. The boat needs TLC but it is setup as I would want it. What should be the final offer price that would be reasonable for the seller and something I will not regret later?

 

[NIGHTIDES]

Is the boat a 1998 as well..??

If so and the boat is rough, $15,000 range. Forget the engine value.

Just my $.02.

 

[seasick]

There are always things you don't see when buying used that pop up. When you do know about issues ( like the compression) that is a red flag. The compression spread is a bad sign and that mechanic is yanking your chain if he states that there are no guidelines for acceptable compression differences. If the hull is good, as stated, consider its value and the cost of a repower.
If as you say, the boat needs TLC ( whatever that means) and the motor is in not so good shape, think about what you want to do: Boat/fish or futz around mechanically.

 

[Rhangrea]

Thanks, you've convinced me to pass on this deal. Repower is not likely in near future, and rebuilding power heads are $10k+ for twins. Additional bottom paint and TLC means missed summer fishing season, it's a pass.
You guys are great, my sincere appreciations for your advices.

 

[NIGHTIDES]

Smart move on the pass.. Good luck on your search.