new , used boat problem!!

[ry3100]

i just bought a 69, sportcraft 23' with mercruiser 140 hp, i took it out for the first time and i could only get 13 mph out of it, an hour later 8 mph and hobbled in at 6 mph, running rough , i would assume a fuel delivery problem but not sure where to start i noticed a drop of oil on bilge pump mounted underneath oil pan, probably unrelated i would assume, when i got home i realized what seem to be alot of oil in flame arrestor, not sure if that could have been restricting air flow? i was out for about 6 hours and went about 20 miles total.

 

[Dunaruna]

Re: new , used boat problem!!

Your homework for tonight is to do a compression test. Note the readings next to the relevent cylinder number and present a written essay to this thread. Punctuation and spelling count for 66% of your SAT .<br /><br />Aldo

 

[deputydawg]

Re: new , used boat problem!!

Yep, do a compression test. I will help you cheat on this test. Run engine to normal operating temp and shut down, disable the ignition system at the coil wire, block the carb and choke open wide. Remove the plugs 1 at a time and check compression. <br />You will be looking for what the number is on all cylinders as well as and most importantly any cylinders that have low compression.<br />The oil you are seeing is probably what we call blow by. The compression is leaking past the rings or the valve guides and seals. The compression is building pressure in the engine block pushing the oil out.<br />You will probably find at least 1 plug fouled with oil, and low compression.<br />Time for a new engine, or a rebuild.

 

[imported_scott_m]

Re: new , used boat problem!!

While I agree the compression test is valid for a baseline diagnostic, I don't think that blow by and worn rings are exactly his problem here...he ran for an hour at 13 MPH, dropped to 8, then 6. If this is a new boat to you and you don't know the maint. history on it, might I suggest after the compression test (assuming all is reasonable) you consider fuel delivery - water seperating filter, anti-siphon valve, carb condition, vent line. Then a full ignition tune would be in order.<br /><br />ry3100 are you boating on Lake Lanier? I kept a boat there for about 10 years before moving to FL.

 

[waterone1@aol.com]

Re: new , used boat problem!!

The part about oil in the flame arrester and only hitting 13 mph, tells me to start with a compression test. I always remove all the plugs then do the test.

 

[imported_scott_m]

Re: new , used boat problem!!

Oh I agree, he does need to do the compression test to get a baseline on where his motor stands, but is it reasonable for his performance to drop off that dramatically over 2-3 hours of use if it is rings and blow-by?<br /><br />ry3100, we're interested in hearing your results!

 

[lowshovel1]

Re: new , used boat problem!!

Water1--------I also remove all plugs for compression test.

 

[Dunaruna]

Re: new , used boat problem!!

Your homework is late, any results yet from the comp test??

 

[deputydawg]

Re: new , used boat problem!!

Yes, I forgot to add that step. Remove all of the plugs first. PAY ATTENTION TO FIRING ORDER!<br /><br />The blowby will probably not be the only problem, but it is very hard to tune an engine with erratic compression. Plus, just buying the boat, now is when the wonder oil or STP will be burning out.

 

[ry3100]

Re: new , used boat problem!!

hey sorry for no reply, haven't had much time lately to respond or work on the boat, yes mack i boat on lanier, or most of the time allatoona, the guy i bought the boat from said he rebuilt the motor and there is 4 hours on it after rebuild but sat about 8 months after he rebuilt it. i will do a compression test this weekend and see what i find, i somehow feel this is a fuel problem though, i just don't know yet. i will report back this weekend. thanks for the help

 

[ry3100]

Re: new , used boat problem!!

ok the motor blew, the exhaust valve was stuck and the keeper came out and on the upstroke of the piston it broke the head and forced the valve through the piston, looks like i'm in for a engine rebuild!

 

[Silvertip]

Re: new , used boat problem!!

I would bet the opposite scenario. The keeper came loose first, the valve dropped, the piston hit it, bent it and jammed it.

 

[rodbolt]

Re: new , used boat problem!!

I bet it had water on the stem and the piston smacked it and then it all fell apart, thats what usually happens, that keeper is good for 6500 RPM without failing.<br /> its usually caused by water in the manifold area. happens a lot with boats.<br /> I have an 03 8.1 I just pulled with the same issue <br />but the guy opted for a new package so I get to play with an 03 8.1 that has about 90 hours on it and one piston is bad <br /><br /> I am really really thinking it would look good in a late 60' early 70's camero with a nash 5spd and a set of 3.73 gears <br />in stock trim its rated at 420HP or so maybe I could get 10 more out of it.