Odd set of problums!!!!!

start off info. 1974 Johnson 70h (70esl74m) on a 1975ish 16.8 ft Caravelle bow rider tri-hull.
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just traded for the boat around first of the year have run it about 6-7 times with the family it has always ran great. At WOT about 31(GPS)
the problems....
time before last when running around ran great for 30 or so min running WOT it just slows down no shacking or cutting off just low rpm's. did this about 2-3 more times went home and changed the plugs they looked nasty took it back out the other day and started doing the same thing except this time it would not come off at most mid rpm range no high.

so now i put a tub under it started her up disconnect the fuel line to run all gas out (going to change the gas and line with new filter and bulb) but when the motor finely stopped it was very hot (3 sec touch at most) messed with a few wire and the alarm went off. (hot)

ok where am i guys should i just replace the water pump and t-stat then go try it out? i can check compression this weekend if needed. but the thing starts and runs so good Till......


thanks...........................

Check/test your engine's heat warning horn..... Key in ON/RUN position (engine NOT running), ground out TAN wire protruding from cylinder head. The warning horn should sound! Does it? If not, find out why as this is the only warning you'll receive if the engine starts to overheat.

Sounds like it's already overheated! Retorque the head bolts to 18 to 20 foot pounds in the following sequence where each number is a head bolt... and retighted all other powerhead bolts as needed.

If water traces are entering the cylinder(s), remove the cylinder head, clean/resurface the sealing areas and install a new head gasket.

13..14
9....10
5.....6
1.....2
4.....3
8.....7
12..11

horn works now wire was loose....

thanks for the heads up on the head bolts there were a lil loose i retorque. but there was no sign of water traces around the head at all.

jokers_toys said:

there was no sign of water traces around the head at all.

Click to expand...

I was speaking of "inside" the cylinders. Should any water traces show up on the plug electrodes... might look like very small fried BB's... keep the failing head gasket scenario in mind.

droped the lower today and it was nasty in there. apparently all the seals have failed. the lower gear oil is nasty milky white. the impeller was bent up real bad. i will finish up this weekend when i am off again