OMC Engine boggin issues...

[drexton311]

New member here and from what I have researched, I have not seen an issue exactly like mine. I hope all the experts here can help!


I recently purchased my first boat, a 1987 Reinell 185. It has a Chevy 305 V-8, carbed, with an OMC Cobra drive. The boat runs like a champ and was well taken care of. BUT, I have had issues every time I take it out. It sometimes will plane out and sometimes it will not. It acts at times like it is bogging down, then clears up and runs fine. However, even at top speed, it only hits about 25 mpg, has hit 30 once and it runs about 3000 RPM at WOT. The reason I am confused, is because if it had the wrong prop, it would never plane out, if it had a spun hub, the same. It also occasionally backfires slightly, but not very often. My next step was to put new fuel filters on it and drain the gas, as this is the same gas that was in it a couple weeks ago when I bought it and I have no idea how old it is. Any ideas? Thanks!


And to clarify, the engine continues to run when it bogs down, it usually doesn't die.

​

 

[Scott Danforth]

Sounds like fuel issues. Your motor only reaching 3000 rpm is far from running like a champ.

Your motor should spin to 4600 - 4800 rpm.

If your throttle is opening fully, your fuel may be bad, or your carb may need rebuilding or you have low compression and the motor is worn out

In addition to fuel filters, change the engine oil and filter, raw water pump and service the outdrive on any new to you boat.

Check if you are getting full throttle travel.

 

[drexton311]

Thanks for the response. I am getting full throttle (motion) at the carb and It is also a brand new carb. Sorry for the confusing wording, the 3000ish RPMs is when it is bogging. I'll look into the other items you mentioned. I am hoping it is just bad gas.

 

[lakenormangal]

I bet there's a little crud that is messing with the jets in the carb. That happens with my 4.3 Cobra.
Dump out that old gas, put in some new, change the filters, but try and use enthanol free gas and also put some Stabil Marine in the new gas. I always use no ethanol fuel and add Marine Stabil to the fuel. If it still does bog down, open up the hatch, remove the air cleaner and close the choke manually, then open it quick, that's what i do to dislodge anything thats in the carb.

Hopefully its as simple as a dirty carb. It sure sounds like it because it will run good then bog down and backfire. It really sounds like a carb issue.
And definately check out your impeller ( raw water pump) and even replace the impeller. They dont last forever ( as I found out the hard way this year.)

And remember, fuel with ethanol is not good for your old boat. I always keep a bottle of marine stabil onboard. Most fuel places on the lake have ethanol free fuel but I still use the stabil. Not taking any chances.

 

[bruceb58]

Fuel with ethanol is fine for his engine. People have this strange idea that ethanol is devil juice!

If it still does bog down, open up the hatch, remove the air cleaner and close the choke manually, then open it quick, that's what i do to dislodge anything thats in the carb.

Closing the choke while the engine is running is a good way to get a backfire flame up through the carb and burn your face....don't do that!

 

[drexton311]

And definately check out your impeller ( raw water pump) and even replace the impeller. They dont last forever ( as I found out the hard way this year.)
QUOTE]

Ok, dumb question, as I said new boat owner here and my experience is on cars. When you say raw water pump do you mean the water pump bolted to the front of the motor or the small pump under the cover on the stern drive, or both? I noticed a little water coming out of the cover so I may have a leaking pump on the stern. Not sure though. Boat seems to run at a good temperature though.

 

[bruceb58]

Raw water pump is on the drive. It is normal for a little water to leak out of there. Comes out a small nipple on the impeller housing.

 

[The Seahag]

i have a 1989 sunbird corsair 175 with a 2.3 litre ford omc out drive, starts up fine, idles good, but when i xcellerate it wants to cut out slightly, it will plane out but even at full throttle, theres some sputtering going on, i changed the fuel/water filter thinking mite be water in there, new plugs and wires, put seafoam in the fuel tank, still does the same thing, some times it clears up so i don't think its anything to serious, could it be the points or condenser thatis giving me grief? any ideas, I WANNA GO SKIING, thanks

 

[HT32BSX115]

some times it clears up so i don't think its anything to serious, could it be the points or condenser thatis giving me grief? any ideas, I WANNA GO SKIING, thanks

Howdy,

Welcome aboard!

It is MUCH better if you start your own thread instead of tagging onto someone else's.

 

[HT32BSX115]

New member here and from what I have researched, I have not seen an issue exactly like mine. I hope all the experts here can help!


I recently purchased my first boat, a 1987 Reinell 185. It has a Chevy 305 V-8, carbed, with an OMC Cobra drive. The boat runs like a champ and was well taken care of. BUT, I have had issues every time I take it out. It sometimes will plane out and sometimes it will not. It acts at times like it is bogging down, then clears up and runs fine. However, even at top speed, it only hits about 25 mpg, has hit 30 once and it runs about 3000 RPM at WOT. The reason I am confused, is because if it had the wrong prop, it would never plane out, if it had a spun hub, the same. It also occasionally backfires slightly, but not very often. My next step was to put new fuel filters on it and drain the gas, as this is the same gas that was in it a couple weeks ago when I bought it and I have no idea how old it is. Any ideas? Thanks!


And to clarify, the engine continues to run when it bogs down, it usually doesn't die.

​

Howdy

Welcome aboard!

Sounds like a fuel problem to me too!

Here's a thread with some suggested things to check!

http://forums.iboats.com/forum/engi...69-must-have-technical-information-for-diyers

Focus particularly on #15 and #8

Cheers,

Rick

 

[drexton311]

Thanks for the tips Rick!

Update. I drained the fuel tank and replaced the fuel filter. I also replaced the fuel filler hose while I was at it since it was old and cracked. The Carb is brand new (Rochester 2bbl, marine, with vacuum choke) and operates (mechanically) to full throttle with no binding and since it was idling correctly (after I adjusted the idle) I am going to leave any more checks on the carb to last. I checked the prop and it is correct per the OMC manual that came with the boat. Judging from some of the posts here, I think and original OMC manual is worth its weight in gold...I bought the boat from the nephew of the original owner so, they cared for it... well, up until a couple years ago.

I plan on re-servicing the stern drive and replacing the raw water impeller as suggested by other fine members of this forum. Besides these things and a good cleaning, anything else you would suggest I do?


NOTE - I do have a question, the fuel smelled like varnish when I drained the fuel filter but there was NO water, I couldn't believe it! When it was dumped out, it "lacquered" the area of the concrete and bowl it came in contact with.

I am hoping the new fuel will fix the issue, will keep you posted.

 

[HT32BSX115]

anything else you would suggest I do?

Well, if you didn't, I would inspect/clean or replace the fuel pickup screen in the tank, replace the anti-siphon check valve and if the fuel fill hose was cracked and defective, I would also replace the fuel vent hose and any flexible fuel lines from the anti-siphon check valve to filter housing.

 

[MRS]

NOTE - I do have a question, the fuel smelled like varnish when I drained the fuel filter but there was NO water, I couldn't believe it! When it was dumped out, it "lacquered" the area of the concrete and bowl it came in contact with.
This means carb rebuilt really old fuel is no good sorry.

 

[drexton311]

Took the boat out today an she ran 3k RPM and about 30-32 MPH when fully planed. It appears that the work I put into it seemed to help as it was much easier to get on plane this time around. Now I have a new concern, she is sluggish out of the hole. I do not think I could get a skier out of the water in her current condition. I was thinking about putting a set of smart tabs on. In addition, she still backfired a few time and even deiseled for a bit, but I am contributing that to the remainder of bad fuel being burned off. Any input? Also does 3k RPM seem low to you guys? Its a 305 with a cobra drive.

 

[HT32BSX115]

Took the boat out today an she ran 3k RPM and about 30-32 MPH when fully planed. .... Also does 3k RPM seem low to you guys? Its a 305 with a cobra drive.

If that was 3000 at WOT, (full throttle) NOT right!......

That engine running properly should turn 4200-4600 RPM @ WOT. And if I were selecting the prop for max RPM (which is how you do it), I would "prop" it to turn 4600 RPM with 3-4 people and full fuel to get the best holeshot for skiing etc.

 

[bruceb58]

What size prop are you using?

 

[drexton311]

The boat came with 3 props, including one that looks to be the original. All three (including the installed prop) are 3 blade 15 x 17. I noticed I get an ocassional back-fire when I have been running for longer periods at WOT.

 

[drexton311]

It also turns out that the previous title on this boat appears to be wrong. The HIN says its a 1988 model, but the previous title lists it as a 1987, so it was titled under my name as an 1987, ever run into this issue before? Something I am missing?

 

[drexton311]

I am not finding the gear ratio anywhere, but it is a OMC cobra I/O model 985271 if that helps.

 

[HT32BSX115]

I am not finding the gear ratio anywhere, but it is a OMC cobra I/O model 985271 if that helps.

Your model number will be something like the following:
574AMFTC 1987
574APARY 1987
574APFTC 1987
574APSRC 1987

Here's an example of ratios

Hard to say what you have because everything could have been changed many times in the last 30 odd years