1980 35 hp evinrude lost power

[Bobdag]

So my 35 hp outboard lost power at wot awhile back. So far I have rebuilt the carb, synced the carb and butterfly, new fuel pump and lines and replaced the gas cap on my tank. After replacing the gas cap because it wasn't venting the motor started running great! For a little while... After a few minutes it would start bogging down again. If I pull the choke out a little it would run a little better but not like it should. I've replaced both plugs and have a nice blue spark. What am I missing?

 

[flyingscott]

Did you clean the carb or just put new parts in it?

 

[Bobdag]

Cleaned everything. Removed the soft plugs and replaced .

 

[oldboat1]

What do you mean by soft plugs, and bogging down? There are lead plugs left over from carb manufacture, and they need to stay in place. If you removed and replaced them, want to be sure you didn't fill any additional openings. "Bogging down" can mean the hull speed slows -- can mean the motor is running on only one cylinder ("dropping" a cylinder). Or is there missing/misfiring?

To test for cylinder drop, you would pull off plug boots one at a time. If you get no change, that cylinder is dead. Hard to safely do at speeds, so one way is to use a timing gun -- no flashing means no spark.

Also get an adjustable spark tester, and check spark that way (typically at idle). Have to measure the spark -- should get about half an inch. Additionally, should check compression.

Think the gas cap might be OK, but not there -- can leave it loose when running, or borrow a known good tank and lines. The problem can also be the clip at the motor (either the motor side or the tank side).

 

[Bobdag]

I meant the lead plugs. To clean the internal passages I removed them and then put a small dab of rtv on the new ones when I installed them. I put a timing light on the wires while the boat was out last night. I have spark on both cylinders. The compression on the motor was 110 on #1 and 105 on #2
I checked fuel flow from the tank to the motor and it seams ok. I replaced the cap because I did a flow check on the can. After awhile the stream of fuel would Peter out. I loosened the cap and the fuel flow picked up again.

 

[oldboat1]

sounds like the idle passaged were cleaned out pretty well. Need to measure spark and get compression readings.

Beyond that, try pumping the primer bulb when it acts up (fuel pump operation). Better running with the choke closed or partially closed can indicate a fuel pump issue or a carb blockage (lean running). Additionally, can try running with the hood removed and see if there is any difference.

Your carb does have a nozzle gasket, and that needs to be in place. And if you used the rubber tipped needle in the float valve, need the wire clip as well. And....need to be sure the h.s. jet on the bottom is squeaky clean -- part of carb cleaning mentioned above. I usually don't take them out (soak and spray).

 

[jimmbo]

Have you pulled the fuel pipe out the tank. Often the filter on the end of it gets a jelly like goo on it. The last bit of throttle really increases the fuel requirements. Does the primer bulb retain its shape or is collapsing?

 

[Bobdag]

sounds like the idle passaged were cleaned out pretty well. Need to measure spark and get compression readings.

Beyond that, try pumping the primer bulb when it acts up (fuel pump operation). Better running with the choke closed or partially closed can indicate a fuel pump issue or a carb blockage (lean running). Additionally, can try running with the hood removed and see if there is any difference.

Your carb does have a nozzle gasket, and that needs to be in place. And if you used the rubber tipped needle in the float valve, need the wire clip as well. And....need to be sure the h.s. jet on the bottom is squeaky clean -- part of carb cleaning mentioned above. I usually don't take them out (soak and spray).

Well it's a new fuel pump. However the new pump didn't come with a new gasket to install on the motor.

 

[jimmbo]

If the fuel pump to block gasket leaks, it is like a leaking vacuum line, the pump will not pump at full capacity. The leak will also cause that cylinder to run lean

 

[Bobdag]

I'm gonna put a little rtv on that gasket and see how it does. How do you check the spark other than pulling the plugs and looking? Please don't tell me you hold onto the wire to check! Lol

 

[Bosunsmate]

Well you can hold on to it, but it wont tell you much.
You need to hold it at least 7/16 gap off the head and check it fires constantly in a repetitive manner.
You can build something with two nail 7/16 apart if thats easier, or you can buy an adjustable gap checker from the shop.
I rtv used gaskets the whole time

 

[jimmbo]

Rtv and gasoline do not like each other, the rtv will deterorate, replacing the gasket is a better choice.

 

[Bobdag]

I'm a mechanic by trade but these boat motors take some getting used to! Lol.
I've rebuilt car motors on down to chainsaws but when it comes to boat motors I'm not that knowledgable.

 

[jimmbo]

I'm a mechanic by trade but these boat motors take some getting used to!

That will make you very dangerous around inboard and stern drive boats

 

[Bobdag]

Haha! Good to know!

 

[Bobdag]

Thank you for the help! I appreciate it immensely!

 

[oldboat1]

I doubt it's the gasket, but sure possible (see you had mentioned a new fuel pump in your first post -- missed that. Just loosening and refitting might be enough to insure the gasket seals. Might make sure the old marks or indentations match up when reused.) And can pick up a replacement gasket, as mentioned, or try some sealant. Check at an auto parts store (Permatex is good -- think it's either number 2 or 5 -- read the label for application). Additionally, if you can borrow a tank and lines, might try that and see if it makes a difference. Pickup screens can get blocked, as mentioned. Need fresh gas and a 50:1 mix with TCW-3 2-cycle oil of your choice.

But do need to check spark with an open air tester (maybe $10 at the auto store). You probably have a compression tester -- need to see what numbers you have.

Also, temp. is always a consideration with outboards. Want to make sure it's pumping water -- if top of the head is too hot to touch, it's too hot. It should run around 140F or so. Over 160F is too hot.

Hope you get it handled. Post results....

 

[Bobdag]

I doubt it's the gasket, but sure possible (see you had mentioned a new fuel pump in your first post -- missed that. Just loosening and refitting might be enough to insure the gasket seals. Might make sure the old marks or indentations match up when reused.) And can pick up a replacement gasket, as mentioned, or try some sealant. Check at an auto parts store (Permatex is good -- think it's either number 2 or 5 -- read the label for application). Additionally, if you can borrow a tank and lines, might try that and see if it makes a difference. Pickup screens can get blocked, as mentioned. Need fresh gas and a 50:1 mix with TCW-3 2-cycle oil of your choice.

But do need to check spark with an open air tester (maybe $10 at the auto store). You probably have a compression tester -- need to see what numbers you have.
Compression is
Also, temp. is always a consideration with outboards. Want to make sure it's pumping water -- if top of the head is too hot to touch, it's too hot. It should run around 140F or so. Over 160F is too hot.

Hope you get it handled. Post results....

Compression is 110 on #1 and 105 on #2
I can put my hand on the thermostat when it's hot. The impeller and water pump housing were replaced towards the end of last season.

 

[oldboat1]

Would look for compression in the mid 120s or so, so current readings appear to me to be on the low side. Maybe try another tester.

 

[jimmbo]

Wedge the carb open when doing the compression test. Do it on a warm engine. Have you done a decarb on it recently? the rings may be sticking a bit.

In 1980 my dad bought the same engine. The boat needed a long shaft, the dealer only had a short shaft in stock, so the extension kit was used. Well, during break-in the engine was running lean and would die when the throttle was opened fully. An inspection showed the fuel line kinked under the carb. During the extension kit install the powerhead was removed to replace the shift shaft and after it was put back together the tech didn't notice the line got kinked. Tried to unkink it and snapped the hose fitting off the carb. Took it back to dealer and they replaced the bottom of the carb. Warrantee of course. 2 yrs later took the engine back for something. When I picked it up, I examined the repair order and found several electric start interlocks were replaced. That was pretty cool, considering it was a rope start engine. After a chat with the dealership GM and the owner, I received several items for my 'inconvenience'. Next day a call to the Commercial Crime division of the RCMP. That dealer is no longer in business, good riddance. It was good little engine, had it for 16 yrs. Sorry for the novel, but the symptoms were similar.