Help Please - Mariner 40hp 2 stroke
Hi guys, great to now be a rib owner. However I'm having a few problems with my first rib. I'll try and keep it concise but give you as much information as possible.
I've had a few boats and 2 stroke engines in the past but I am not knowledgable at all really in these kind of things so apologies for any poor descriptions of parts etc.
Boat - Olmec Rib (Apparantley one of a kind, designed and built by the chap who used to own olmec before it went bust). Previous owner bought it new from him around 9 years ago.
Engine - 40hp Mariner 2 stroke (Apparantley ex-RNLI) Bought by the previous owner when he bought the rib around 9 years ago. Paired with quicksilver remotes. Pull start.
Problem - Engine is cutting out randomly (at lower speeds it seems - i.e pottering out of the marina). As if it was out of fuel in a way, just dies very quickly.
So here's the information:
Took it out 2 weeks ago for its first trip.
1) Filled plastic tank at front of boat with fresh fuel and added appropriate amount of oil mix (50:1) as recommended by previous owner.
2) Did all the usual (prime with bulb, set revs etc) Its started second pull, smoked for a little time then settled in.
3) Took it for a 30 minute run. A mix of pottering but mostly cruising between 6-12 knots. Got back to marina, turned off and got my parents aboard.
4) Set back out at idle speed and engine cut out very suddenly. Luckily another rib spotted us and towed us back in.
5) Got it started again but was more difficult than normal. Tried again and every time we went pottering around it cut out within a few minutes. Around 6-7 times in total. Gave up and recovered the boat.
Went back to the lakes a week later and tried again:
1) On the driveway I checked the following:
Fuel lines and bulb - all seemed fine
Small fuel reservoir on engine where fuel is pumped in by bulb - bulb seemed to prime it fine and it stayed full with fuel when engine was running with muffs.
Boat idled fine on driveway for 10 mins without cutting out once.
2) Launched it and went out with parents for 30 min run. Went fine just as last times first outing.
3) Back to marina, turned off. Went back out for a run half an hour later and engine started cutting out again. This happened around 5 times and in the end I gave up again.
I removed engine hood right after it cut out and fuel reservoir was full and everything looked ok. Therefore my initial thought of fuel starvation/blockage from tank to engine doesn't seem as likely now. Although the motor did seem hot. There is a black metal plate that i was told if this gets hot that its bad news where water flows through. This was fairly hot and I couldnt keep my hand on.
However when I got it started again I went back at a good pace - around 5 minutes and when moving at pace it didn't cut out. Although it did possible sound a touch more noisy than before. However when back I checked the plate and having gone faster for 5 minutes it was now pretty cool.
I.e The faster I go, the cooler the engine and the less it cuts out.
It doesn't seem to idle too low and the previous owner (Who did seem very reliable/nice ex engineer) is insistant that this has never happened to him in his 9 years ownership and believes it can only be something small/silly. Pumps water very well.
Any questions just ask, Sorry if i have missed anything. Can't seem to figure it out at all - maybe a carb clean would help ??