Idles, no power

[yamjer]

Hello all. I have a 1988 doral with a 350 mercruiser 260 hp engine. I was motoring to my slip and out of the blue I lost my speed. Limped to slip. I have what seems like a knocking/clacking sound from motor. I pulled valve covers and reseated all. Noise still there. Took boat for short run (3/4 minutes) and could not gain any speed. Is my crank gone? Bearings? Is there any way to check without pulling motor?

 

[alldodge]

If it's banging like a hammer then most likely it spun a rod bearing

pulled valve covers and reseated all.

What does this mean? reseated all

Could do a compression test to find out if it might be a valve issue

 

[yamjer]

If it's banging like a hammer then most likely it spun a rod bearing


What does this mean? reseated all

Could do a compression test to find out if it might be a valve issue

The noise sounded like a valve problem. Took valve covers off, removed rockers and rods to check if any bent or loose. Put back together. None of the rods are bent. I also think bearing but not sure I'm up for the challenge.

 

[alldodge]

There are some you tube vids that has the sound of a rod knocking

Again, if you have good compression then it's not a valve

 

[yamjer]

,k

There are some you tube vids that has the sound of a rod knocking

Again, if you have good compression then it's not a valve

Thanks. Thats next task.

 

[Bondo]

Hello all. I have a 1988 doral with a 350 mercruiser 260 hp engine. I was motoring to my slip and out of the blue I lost my speed. Limped to slip. I have what seems like a knocking/clacking sound from motor. I pulled valve covers and reseated all. Noise still there. Took boat for short run (3/4 minutes) and could not gain any speed. Is my crank gone? Bearings? Is there any way to check without pulling motor?

Ayuh,..... I wouldn't discount a drive problem either,.....

 

[yamjer]

I was ready to change my outdrive (I have a couple in my garage) but the noise from my motor were edging me to think that was my problem. Thanks for responding.

 

[ROY WILLIAMS]

I was ready to change my outdrive (I have a couple in my garage) but the noise from my motor were edging me to think that was my problem. Thanks for responding.

did the engine oil ? 40wt , 20w-40wt ...Mercruiser engine oil .

 

[yamjer]

did the engine oil ? 40wt , 20w-40wt ...Mercruiser engine oil .

Apologies. Just made it back to boat. Yes changed oil with mercruiser oil.

 

[yamjer]

Did compression test. #1 -145 #2-90
#3- 65. #4-135
#5-50. #6-65
#7-135. #8-135
Would think head gasket port side but geez not sure what to make of these. Will bring a turkey baster and try and inject a tbsp of oil for another round of compression tests.

 

[Bondo]

Did compression test. #1 -145 #2-90
#3- 65. #4-135
#5-50. #6-65
#7-135. #8-135
Would think head gasket port side but geez not sure what to make of these. Will bring a turkey baster and try and inject a tbsp of oil for another round of compression tests.

Ayuh,..... Pull the motor,...... You've got serious problems,......

Or do a leak-down test to see whether it's rings or valves,....

 

[yamjer]

Since its almost end of season here, will try leak down test. But I agree. I will probably be looking for a motor.

 

[ROY WILLIAMS]

Did compression test. #1 -145 #2-90
#3- 65. #4-135
#5-50. #6-65
#7-135. #8-135
Would think head gasket port side but geez not sure what to make of these. Will bring a turkey baster and try and inject a tbsp of oil for another round of compression tests.

the flat taps .... the gasoline higher and the adjusting it timing ....
I was the marvel mystery oil in the fall spark plugs out one OZ. did the winter maintenance . did the rusted combustion area MMO .....

 

[Scott Danforth]

Did compression test. #1 -145 #2-90
#3- 65. #4-135
#5-50. #6-65
#7-135. #8-135
Would think head gasket port side but geez not sure what to make of these. Will bring a turkey baster and try and inject a tbsp of oil for another round of compression tests.

since 150 psi is a new motor
you have 4 pistons trying their best at 90% power and 4 pistons that are simply causing drag.

great opportunity to build a 377 or 383 since it looks like you need a new motor.

 

[tank1949]

Hello all. I have a 1988 doral with a 350 mercruiser 260 hp engine. I was motoring to my slip and out of the blue I lost my speed. Limped to slip. I have what seems like a knocking/clacking sound from motor. I pulled valve covers and reseated all. Noise still there. Took boat for short run (3/4 minutes) and could not gain any speed. Is my crank gone? Bearings? Is there any way to check without pulling motor?

If by "reseating," you meant adjusted volves then do compression test to pinpoint area. Examine plugs. If rust or water, you may have to tear motor apart and buy new exhaust manifolds or risers. However, you may have spun a bearing.

 

[tank1949]

Did compression test. #1 -145 #2-90
#3- 65. #4-135
#5-50. #6-65
#7-135. #8-135
Would think head gasket port side but geez not sure what to make of these. Will bring a turkey baster and try and inject a tbsp of oil for another round of compression tests.

I had a compression tester malfunction on me one time. Get a second tester and see if readings are the same. If so I expect you will have to repower. If salt used, replace block.